Which game you prefer really depends on whether you want to race on standard tracks & become first of the bunch, or wanna ride against a time limit. Since I like the last one, I vote Lotus II. It also loads fast and comes on one disk.
Lotus I I never played on my original Amiga and Lotus III is more a remix of I and II. Also the tunes you can select from the radio in III were crap compared with the tunes in Jaguar XJ 220 - a game released 2 months earlier.