It’s easier for me to say what I don’t like… modern GP tracks like Yas Marina and COTA.
I’m not a fan of tracks dominated by harsh corners. The best courses are ones with tricky, gentle corners leading onto straights, which create overtaking possibilities. A good example of this is turn 5 at Road Atlanta, a turn that’s easy to screw up, but if you nail it and the next car up doesn’t… you get a position. I’m also a fan of turn 7 at Lime Rock Park for the same reason.
As stated by many others, flow. I like tracks that were originally laid down to flow around the natural landscape surrounding them, like Laguna (the original layout would be awesome in a game), Sonoma, Roads America & Atlanta, Mugello, Suzuka, Brands Hatch, you get the idea. Even a good street circuit can have good flow. Can’t stand most modern GP circuits, all start and stop, no flow. Most of them are so featureless I actually get lost on them occasionally. I hate to say it, but I don’t like most of the original tracks that I’ve played in the two Forzas (4 & 6) I’ve played. Maple Valley was okay, with a nice flow to it, didn’t care for Camino. Really, REALLY hated Fujimi. Both Rio and Prague make me want to drive Jaguars like a Bond villain, they are beautifully done environments, I just don’t really care to race on them.
It would actually be very interesting to know what tracks people play the most when they get to pick the location, in free play and in private lobbies.
I love tracks that have a good mix of fast sweeping corners and tight hairpins at the end of straights to test you under brakes.
My favourite track for a long time has been Laguna Seca, the tight hairpin at the bottom of the sweeping straight is wicked if you miss your braking line and the apex through the corkscrew is beautiful if you get it just right. There are also those beautiful fast corners around the back where you can nail it if you get your apex and carry a ton of speed through the straights, but they give you a headache if you run wide and end up in the sand.
I don’t really enjoy some of the GP circuits like Yas Marina, as beautiful as the circuit is racing at night. Give me grass and gravel to keep me honest and on the track any day of the week.
I would love to see a return for tracks like Suzuka but I’m pretty happy most of the circuits we have now.
I’m hoping that if they do introduce any more of the ‘dream’ tracks like Prague or Rio, they look to create something a bit more open where it feels more like a racetrack rather than a street race. Give us those fast corners but don’t give us barriers to stop us running wide, keep that heart rate up!
Fujimi Kaido was a great track to drive but a terrible track to race, it had elevation change and a ton of unique corners, but it was too narrow to actually race on.
As for what makes a good race track, I am not a fan of 90* corners. I like chicanes, I like elevation changes, I like an occasional odd bump or two that upsets the car, I like tracks that flow nicely, and they should be wide enough to facilitate passing, good scenery is a plus, I like bridges and tunnels.
Some of my favorite tracks in FM6:
Bernese Alps, nice flowing track, good scenery, I love the small jump just before/after the 3 S curves by the start/finish line and those 3 S curves are also great fun and they are a nice elevation change
Brands Hatch, flows nice, it is wide, there are also some small elevation changes
Circuit de Catlunya, I am just fast on this track for some reason, it is nice and wide, with high speed straights and some changing radius corners
Spa, hate the starting hair pin corners but after that the elevation and long sweeping corners are great
Lime Rock, love the hill on the back stretch of the track, it is also an easy track to drift
Leguna Seca, the cork screw is fun and the track is nice and wide
Mount Panorama is fun to drive but I don’t like to race on it, it is too narrow for racing, the tight corners and elevation change make it a fun track to drive
The Ring falls into the same category, great track for the elevation and tight corners but too narrow for racing
Prague and Rio are both fun for their elevation and chicanes, nice scenery, and the huge sweeping corners, there is also one spot you can catch a little air routinely on Rio
Road Atlanta is good for the elevation and the S turns after the start line
Sonoma is good for the elevation and several S turns
Watkins Glen is fun for the long sweeping corners and the chicane
Tracks I miss from FM4
Sunset Peninsula, various chicanes and the high speed ring section
Camino Viejo, had some great bumps in it that would upset the car and good scenery
Iberian International Circuit, had some nice sweeping corners and that jump on the back stretch. Also like the version connected to Camino Viejo with the huge elevation change switch backs.
Ladera Test track had some nice chicane like corners
Maple Valley had some nice sweeping corners, elevation change, and a small jump by the covered bridge, the scenery was also good
Mugello had nice sweeping corners
Rally di Positano, was another track that was fun to drive but not to race. Small jump, great scenery, and nice tight corners, but too narrow for racing.
Sedona had the small jump, and nice sweeping corners.
The Sidewinder track was also fun to drive on but not to race on, it was just over the top on the corners and there was the switch back section that did some elevation.
Wow I agree 100% with almost all of this.
Except Sedona. I’ve always hated that track.
A great track is one where I’m faster than my friends.
A bad track is one where my friends are faster than me.
Another fan of flowing tracks here,sweeping corners,with a nice view as you come down a hill,not 90 degree turns where you have to stand on the brakes for seconds before.
I did enjoy the fantasy tracks from FM4, I wonder why they cant be in 6,its not like they have to be laser scanned!
Well, I know for a fact what makes a track bad - just look at Long Beach. 
Slow, tight turns with no run-offs and barely any opportunities to overtake. Drivatars create a pile-up in the first turn every race without fail. Maybe over the course of a longer race the track might have better use but in Forza’s three-laps-to-reach-podium format it’s the track I dread having to race on.
I believe that one of the Grand Prix drivers of the time back in the late '90s criticized the modern Nurburgring by calling it an “unimaginative circuit that had too many chicanes and not enough good corners” or something to that effect.
Yeah, I don’t much like that circuit either. I prefer Hockenheim.
While I agree with most of what everyone has said in terms of driving, for racimg I completely disagree with most of this. Flow usually makes for bad racing, to me the very technical and straights into sharp hairpins make the best racing.
Tracks like alps, lime rock, watkins make for really boring rackng in my oppinion. On those tracks all you have to do is stick to the racing line and the chances you get passed are slim to none.
As much as everyone has claimed they hate it if u can get people not to cut the track yas is actually a very good race circuit. There’s hard braking zones fast straights fairly fast chicanes, high speed sweeper.
When it comes to just lapping by urself I’m with everyone else tho.
So a track like Spa, Silverstone etc is worse for racing than Yas Marina? Have you ever watched the Abu Dhabi Grand Prix before?
No that’s not what I was saying. I meant more of the momentum type tracks lIke alps, lrp, watkins. While they are all good tracks to drive I think they are pretty poor tracks for racing. No verity to the corners really and nowhere to pass. Atleast at Abu Dhabi there’s a mix of everything and Places where u can attempt passes. Alps and the other tracks really only have one possible line if u are off of it you aren’t going to be able to make passes.
So many tracks are large go-kart tracks.A good track to me needs a couple 200+ mph straights first of all.
200+ mph
Elevation changes (for roller coaster feeling fun[even in a virtual game])
Hard braking sharp turns for passing
Different sizes/speed of twisties
1 esses
What makes a track great for me :
For me its about coming back lap after lap to better your lap time. Especially at a track like Bathurst, where across the top of the Mountain you test your level of commitment each time. The better the flow you have corner to corner, the more exciting the circuit is.
A list of my opinions:
I like tracks that keep you on your toes, Bathurst is fun but really isnt good for sprint races. I like tracks that have lots of variety and complexity, double apex corners, late apex corners, fast switch backs where the car is on edge. Elevation can make all the difference too, can make for some exiting turns even the ocasuonal of camber turn can be pretty fun. More or less I’m a fan of tracks that you could take a stock junk car and still have some fun with it
Road Atlanta is a perfect example - it tests the car and the driver, There’s 3 or 4 passing zones, You can run many types of tunes (All-round, moderate), and it flows beautifully, especially in sector 1
One track that I’m downright sick of is that snow track. Also, tracks that leave hardly any room for passing like Watkins Glenn.
The tracks that I love are ones like Le Mans, Road America, Road Atlanta, Nurburgring, Sebring, and Laguna Seca. It’s a shame the S class lobby racing is EXTREMELY limited in tracks, and on some of those tracks, it’s always night time or raining.