Truth be told, I prefer to play platformers on a TV. There are moments when that isn't possible, though--and in those moments I pull out my trusty GameBoy Advance (or DS, depending on the situation) and insert one of the following cartridges.
3. Donkey Kong (GB Color)--Considering the quality of this title, it's crazy that Nintendo hasn't remade it once or even twice. (Actually, it seems they planned on releasing a remake of sorts, titled Donkey Kong Plus, for the GameBoy Advance, but canned it in favor of the similar-but-not-quite-the-same Mario vs. Donkey Kong.) Until they do, I'll be playing this classic platformer-puzzler combo on a regular basis.
4. Drill Dozer (GameBoy Advance)--Well, well, well ... what do we have here? Another platformer with a female protagonist--and it doesn't suck! Actually, it's the complete opposite of sucky. Like the aforementioned Balloon Kid, Drill Dozer turns the platformer genre on its ear, although this game accomplishes that feat with a gigantic drill instead of a bunch of balloons.(Fun fact: This developer of this title, Game Freak, also develops Nintendo's Pokémon games.)
5. Kirby Canvas Curse (DS)--When the crew over at 1UP.com reviewed this title, they called it "the DS's first great game." The guys and gals at IGN.com, on the other hand, hailed it as "incredibly innovative." Unfortunately, the critical acclaim didn't have much of an affect on consumer interest and it sold less than 150,000 copies (in the U.S.) in its first two months. If you see a copy (new or used) out in the wild, do yourself and your DS a favor and pick it up--you'll be glad you did.