Top 10 Games from each Nintendo handheld

Gameboy + Color
1 -- Pokemon Gold/Silver
2 -- Zelda: Link's Awakening
3 -- Super Mario Land 2: 6 Golden Coins
4 -- Pokemon Red/Blue
5 -- Zelda: Oracle of Ages
6 -- Zelda: Oracle of Seasons
7 -- Super Mario Land
8 -- Tetris
9 -- Wario Land 3
10 -- Kirby Dream Land 2

Gameboy Advance
1 -- Advance Wars 2: Black Hole Rising
2 -- Fire Emblem
3 -- Fire Emblem: The Sacred Stones
4 -- Advance Wars
5 -- Zelda: The Minish Cap
6 -- Mario Kart: Super Circuit
7 -- Metroid: Zero Mission
8 -- Mario Golf
9 -- Final Fantasy Tactics Advanced
10 -- Pokemon Ruby/Sapphire

Nintendo DS
1 -- Phoenix Wright: Ace Attorney
2 -- Advance Wars: Dual Strike
3 -- The World Ends With You
4 -- New Super Mario Bros.
5 -- Mario & Luigi: Bowser's Inside Story
6 -- Trauma Center: Under the Knife
7 -- Mario Kart DS
8 -- Nintendogs
9 -- Zelda: Phantom Hourglass
10 -- Zelda: Spirit Tracks

Nintendo 3DS
1 -- Zelda: A Link Between Worlds
2 -- Animal Crossing: New Leaf
3 -- Super Mario 3D Land
4 -- Professor Layton & the Azryan Village
5 -- Zelda: Majora's Mask 3DS
6 -- Super Smash Bros. 3DS
7 -- Fire Emblem: Awakening
8 -- Pokemon X
9 -- Mario Kart 7
10 -- Zelda: Triforce Heroes

Alright, not going to include 3DS since it's not legacy and still has a lot of games coming out for it. (and others I'm behind on and haven't played yet) No particular order.

GB/GBC:
Super Mario Land 2: 6 Golden Coins
Dragon Warrior III
Pokemon Blue/Red/Yellow
Metal Gear Solid
Super Mario Bros. Deluxe
Gargoyle's Quest
Bionic Commando: Elite Forces
Wario Land 3
The Legend of Zelda: Link's Awakening DX
Pokemon Pinball

GBA:
Advance Wars
Tactics Ogre: The Knight of Lodis
Shining Force: Resurrection of the Dark Dragon
Astro Boy: Omega Factor
Fire Emblem
Fire Emblem: The Sacred Stones
Drill Dozer
Super Mario Advance series (as to not fill the list with a bunch of ports)
Metroid: Zero Mission
Castlevania series (can never decide which of the three I really like best)

DS:
Advance Wars: Dual Strike
Advance Wars: Days of Ruin
Kirby: Canvas Curse
Castlevania: Order of Ecclesia
Chrono Trigger
Super Princess Peach
Mario Kart DS
Mega Man Zero Collection
Retro Game Challenge
Dragon Quest V: Hand of the Heavenly Bride

Good picks all around: Canvas Curse and the Castlevania games would be right around the corner on my lists.

A Link Between Worlds was good, but Fire Emblem was the best game I've played on 3DS. Also I really enjoyed Pokemon TCG on Gameboy Color and the FF6 remake for Advance. Just so many quality games across the systems.

I play every game handheld. Don't have any favorites