Without a doubt:
Infestation! -- Such a cool idea well ahead of its time, plagued by a lack of enemies and really slow 3D graphics. With a robust redesign, this game would be KILLER on new hardware!
Armour Geddon -- Big, deep, lots of vehicles, "multitasking" gameplay, real time events (day & night)... the list goes on.
Day of the Viper -- Infestation meets Dungeon Master, I think. A resource management game to heart.
Log!cal -- The ultimate marbles game. Maybe a freebee AmigaDE version? But, it has to have a great soundtrack, like the original game.
Sideshow -- A little known title. Visit a carnival and play booth games for tickets and food. Harmless, addictive fun! I still play this one a lot on my 1200.
Stunt Car Racer -- For sure! It amazes me that with all of today's hyper 3D technology and sophisticated physics engines, that nobody can make a stunt racing game! What ever happened to classics like SCR, and the arcade version of Hard Drivin'? Everyone just wants to make the next cheezy verion of Need for Speed or Test Drive! AAAAAARRGH!
Wings -- But, it must have a great story. Red Baron II was a bit TOO realistic to be fun, Knights of the Sky was too cheezy, and Dawn Patrol was impossible to play. Wings was just classic gaming at its finest!
Titus the Fox -- No, no... just kidding!