well i'll start with a system you didn't list

N-Gage: Pathway to Glory (a great game as was its sequel and i found myself playing it whenever i had a free moment)
Lynx: Rampart (maybe not the best version of the game but my favorite and most played game for the system)
Game Gear: Mortal Kombat (again the best way to gage my favorite games for system is as time spent with them. probably played this more than anything else)
Neo Geo Pocket: SNK vs. Capcom: Match of the Millennium (great game)
DS: Professor Layton and the Curious Village (one of my favorite games now)