I had a ton of fun with NFS2:SE. All the cheat codes to drive logs and outhouses were over the top and super funny. Me and my friends had hours of laughing. The school busses had crazy physics when crashed head on.
BUT, the game I had most fun in was midtown madness 2. I bought a PC gamer magazine back in the day and it had that review in it. I think it only got a mid-70 score but it looked so awesome! For months I contemplated getting it because $30 was a lot of money back then. I don't regret it at all.
There was this one building you could drive up and we would have king of the hill battles on top of it. All with no chat. You just knew what to do by watching others.
THEN the mods were discovered. People made cities in the sky and added jumps EVERYWHERE and made it so you could drive on water and made super cars and made.. ..and... and... and!!!
There was in multiplayer a game mode called cops and robbers where the robber would try to get the gold and then the cops would try to ram him and make him drop the gold. This was alright, but an alternate was BUS cops and robbers. Everyone was in city busses that were slow in every way and you had to be a lot more strategic in your pathing and speed in order to not get hit or hit the other. When you have 5 busses converging on one point it can become very chaotic.
But, my favorite 'real' racing game is Grid. NFS: High stakes is not far behind. had tons of fun with that one too.