According to some consoles:
- Nintendo
Mappy Kids (just for the catchy theme in stage 2, listening for an hour).
Contra and Super Contra.
- Super Nintendo
Dragon Quest 3.
Ganbare Goemon 4 (Yae's levels are a good platformer design).
Megaman & Bass and Megaman X Trilogy (for a quick game assault).
Super Metroid.
Demon's Crest (the 4 Endings).
ActRaiser 1 (love the simulation mode).
Super Adventure Island 2 (Feels good ?)
- Nintendo 64
Bomberman Hero (this is my favorite Bomberman,
because you can jump and throw bombs, like no tomorrow, good music and fine gameplay, challenging).
Kirby 64 - The Crystal Shards (beyond completing it, always trying to get all of the 81 Info cards).
Eltale Monsters (Japanese Quest 64), because I'm always grinding to get max experience.
- Nintendo Gamecube
Megaman Network Transmission.
Paper Mario - The Thousand-Year Door.
Final Fantasy Crystal Chronicles (getting all Artifacts and weapons as possible).
- Nintendo Wii
Super Smash Brothers Brawl (D-Pad blessed times, getting almost everything).
- WiiWare
Final Fantasy 4 - The After Years (with all DLC).
Megaman 9 & 10.
Pokémon Rumble.
- GameBoy
(Makai Toushi) SaGa Trilogy.
Super Mario Land 2 - The 6 Golden Coins (for the hidden levels to discover).
Kirby's Block Ball (specially for the Stage 5 theme).
- GameBoy Color
Dragon Quest (Warrior) Monsters 1 & 2 (for library completion's sake, specially the second).
The Legend of Zelda - Oracle of Seasons and Ages (most time in Ages, and trying to get the 64 rings).
- GameBoy Advance
Castlevania Trilogy (specially Aria of Sorrow).
Final Fantasy 2 and 5 (grinding squared, for the first one).
Golden Sun - The Lost Age (with all Djinns, to Anemos Temple).
Lufia - The Ruins of Lore (for getting everything and making some databases for the monsters families and its evolutions).
Megaman Zero 4 (mostly, strategically for the parts, trying to get S Ranking every time).
Metroid - Zero Mission and Fusion (mostly Zero Mission).
The Legend of Zelda - A Link to the Past.
- Nintendo Dual Screen
Dragon Quest 4 and 9 (so many times, I'm addicted to this one).
Puzzle Quest - Challenge of the Warriors (both endings).
My World, My Way (to complete all encyclopedias).
Kirby - Mouse Attack and Super Star Ultra.
Spore Creatures.
Pokémon White.
- Nintendo 3DS
Fire Emblem - Awakening (250+ hours, and repeating it, after an accidental Micro SD Card formatting).
Miitopia (almost the same, as above).
The Legend of Zelda - A Link Between Worlds (for Streetpass Challenges' sake, Normal and Hero Mode. Because of the above with FE - A, played it at least four times).
Bravely Default and Second (same case as above).
Dragon Quest Monsters - Joker 3 (Original and Professional, both of them, complete bestiaries).
Dragon Quest (remakes) 7 (for the 417 monsters and monster jobs).
& 8 (almost twice, yes, this one is same case like FE - A).
- Sega Genesis/Master System.
Castlevania Bloodlines.
Contra Hard Corps.
El Viento.
Gunstar Heroes.
Monster World 4 (the one with blue haired hero, supposedly called Shion).
Shinobi 3 - Revenge of the Ninja Master (for the Izayoi Theme).
- PlayStation 1
Final Fantasy Trilogy (7, 8 & 9).
Dragon Quest 7 (again, because of some good time back in 2015).
Megaman X Trilogy (specially X6, rescuing all 128 Reploids).
- PlayStation 2
Shining Force EXA.
Castlevania - Curse of Darkness (I loved the crafting system).
- PlayStation Portable
Castlevania - Dracula X Chronicles (mostly, for unlocking and playing the Symphony of the Night Easter Egg, recommended).
Dissidia - Final Fantasy (almost endless to unlock everything or rather maxing out every character, aiming again for Lufenia's Equipment).
...I can tell more, but I'm finishing with two of them... Via phone.