Quality gameplay and nostalgia are the main factors motivating me when I boot up my favorite platformers. Some platformers are made of epic amounts of win. These games basically forces you into completing them every other year or so.

List platformers you find yourself completing over and over and over again (my favs below).

IMO Mega Man 2 = Quality Gameplay, Epic Music, Creative Level Design, Cool Bosses and Good Gfxs!

Every main Mario game ever. SMB, SMB2 (non-JP), SMB3, SMW, SMW2, SM64, SMS, and SMG.

If Kirby Power Paintbrush counts then that too.

ratchet and clank 3 and TOD i replayed 3 or 4 times.

All main Mario and Kirby games. SMB, SMB2, SMB3, SMW, SM64, SMS, SMG. Also KD, KD2, KA, KD3, KSS, K64, KaTAM, KSqS.

For me the Ratchet & Clank games have had the most replay value among platforming games.

Did you miss out Yoshi's Island and Power Paintbrush for a reason?

 Yoshi's Island has quite a bit of Replay value but I think the games in my post have more replay value.  My opinion, of course.

I managed to collect all the red coins in Super Mario World 2: Yoshi's Island. A real 'gamer chore', but it was worth it. SMW2:YI is the most difficult main franchise Super Mario game in my opinion. :/

all the banjo games, alll the donkey kong country games and kameo.

crash bandicoot well ps1 ones, and ratchet and clank has amazing replayabilty with its different modes after u finish the game, not to mention the awesome arena battles with all those insane bosses