I support Sonic CD DLC Desert Dazzle and Final Fever.
Generations or sonic 1
Representation? probably Generations.
And just to say, Speed isn't what Sonic is all about, it never was.
Even with the modern games and even Unleashed.
As fast as Sonic could run in Unleashed, there were still many things to change the pace~ The were-hog, the hub-worlds among other things.
which game "should" as it represents one of the best in the series:
2D : S3&K
which game sega will probably "say" does
3D: Generations or whichever is the latest "non gimik and multiplatform" game ( eg not the wii/DS only ones)