[Bobboau]

kapow!

[Cobra]

w00tage!

[Bobboau]

I think delta is probly the best, though it helps to have a level select save state (kega format) to get the most out of any of these. and just because I'm such a nice guy, I'll zip one up for you with such a save state.
delta has a number of levels added to it that were made from a handfull of partaly completed levels found in a sonic 2 beta that was discovered in a chinees rom shop, if you have any interest in the developments of sonic 2 do some googleage on the sonic 2 beta, they found some realy neat stuff.

meh, zip was too big with the save state, it's the same code as the origonal game.

[Clave]

I like Ecco a lot, and it also had awesome graphics and sound for the time.  But on the downside, it was HARD!  the only game I have played that was harder than Ecco was The Immortal, which was basically impossible to complete by normal humans....