Lotus, the first one. The 2-player mode is just brilliant. Lotus 2 was all that Outrun should have been. For 1-player, L2 was amazing. However: I still prefer L1 even for 1-player, it's more challenging.
Has anyone noticed this little thing I remember after all these years? In L1, 1-player mode, the scrolling is great and super-smooth. But when 2-player mode is engaged, the scrolling sufferred just a tiny bit enough to spoil some of the 'wow' factor present in 1-player mode...
And L3 was a complete disappointment, I can't even compare it to the Turrican 3 disappointment, because that was actually a good game. L3 wasn't.