Lotus 1 is the most fun with it's "must get within top 10 each race" and is very fast. Pity the cars are the same colour. I played this game an enormous number of times with my brother competing to win the championship on hard. It's good to see a game that makes you want to play through it on harder levels. Nothing better than seeing your human opponent smash into a solid barrier and come to a complete halt while you fly past!
Lotus 2 is great but I don't like the checkpoint thing as much as Lotus 1. The graphics are the best of the series but it's silly that you can just bounce off everything.
Lotus 3 is just naff - the road goes backwards most of the time, stupid futuristic turbo zones, road is so wide on some tracks you can just drive in a straight line, and the track editor is garbage. Lotus 3 was a complete letdown for me.