Does any one know what the best all around car in the game is without upgrades, and which ones have the best acceleration and so forth with every category? I have often wondered this.

I would vote for the Ferrari Enzo. With no upgrades and a bit of tuning (to suit your driving), it competes well with maxed out. full aero cars in S class

It depends on what class you want. For S, the Enzo isn’t a bad choice unupgraded.