Bubble Bobble Old and New (Import, because I don't know if this one came out in the USA)
Super Puzzle Bobble Advance (It's ok, but still fun to have, I'm still sticking with the original)
Konami's Krazy Racers aka "Wai Wai Racing" (Awesome clone of Mario Kart, plus being the first to use the Mario Kart Mode 7 style. Features characters like Dracula from CastleVania, Cyber Ninja from MGS, The Octapus from Parodius, and Goemon from Mystical Ninja, hell Vic Viper the space ship is a hidden character too!)
Gradius Galaxies (Hard, but many people passed it up, I love it)
Lunar Legends (Solid RPG port, with a complete twist in the storyline compared to Sega CD and the PSX verisons)
Konami's Arcade Advance (Picked this up for $10 at TRU last X-mas, and I will say, having Rush N' Attack, Frogger, Yie Ar Kung Fu, Time Pilot, Gyruss, and Scramble) was a worthy buy, plus they added in "Advance" modes on some, so the old games get a slight upgrade via codes
Pac-Man Collection <--- this was solid...especially for choosing Pac-Attack as a choice of game...I really dig the puzzler
Columns Crown <-- another solid Puzzle game
DOOM 1 and 2 for GBA <--- 1 is a port from the Atair Jaguar, very nicely done, they even added DeathMatch and Co-op for 4 player. I'm still trying to hunt down Doom 2
Wolfenstien 3D <--- badass port of the classic PC game...all the missions too!
Super Ghouls N' Ghost <--- It's cheap, it's a classic..but..this is like a grand master challenge..you get rewards for finishing the levels with the golden armor..
Tony Hawk 2 for GBA...sure I hate sports games..but I had my moments of Skate Boarding games since days of "Skate or Die"...but this GBA port...very nice to have around if you're super bored...Im surprised how well the game handles
Onimusha Tactics <-- this is really good I hear
Sim City 2000 <--- this came out of nowhere back in December..but I love the original classic...it's like $15-20
Wario Land 4 <-- no one hardly talks about this one anymore...but god it was fun, because it just wasn't a port..it was totally original
Duke Nukem Advance <--- This was a lovely port, hardcore Duke 3D fans will love this one, i tried it for 5mins...just damn...everything is in tact..