I recently did a video on my top 10 co-op games. I'm not really an online gamer, so my favorites are mostly retro platformers and beat 'em ups you could play together in the same room, but I did include some modern games too. Anyway, have a look at my video at let me know your favorites too!

10. Sonic the Hedgehog 2 (Megadrive)
9. Metal Slug (Neo Geo, PSX, PS2, etc)
8. Phantasy Star Online (Dreamcast, Gamecube, PC)
7. Dark Souls (PS3)
6. Streets of Rage 2 (Megadrive)
5. Chip 'n Dale Rescue Rangers (NES)
4. Journey (PS3, PS4)
3. Secret of Mana (SNES)
2. Donkey Kong Returns (Wii)
1. Super Mario 3D World (Wii U)

I'm not an online gamer, either. I rarely play co-op as well, just single player.

Sanctum 2
Borderlands 2
Black Ops (Zombies)
Journey

AD&D: Shadow Over Mystara

Battle Circuit

Cadillac & Dinosaurs

Seiken Densetsu 3

Snow Bros.

Super Pang!

Gunstar Heroes

Midnight Wanderers

Ikaruga

New Super Mario Bros Wii

Retro: Streets of Rage 2

Last-gen: Kirby's Epic Yarn & Trauma Center: New Blood

Current-gen: Super Mario 3D World

In that case you're quite similar to me. Still, in some ocassions co-op can be great! Like, Super Mario 3D World totally blew my mind and was my main reason for starting this topic, have you ever tried it?

TomaTito, good taste!

Ratchet: Deadlocked. It was way worse than the previous 2 without the co-op but if you could get someone to play through with you it was actually a blast

Journey. Just super fun to randomly find someone and have to adapt to not using words. Creates great replay value as I've gotten more hours out of a 2 hour long game than any online mode I've ever played

No Man's Sky. My God what an awesome experience. Me and my pals met up and started establishing our own galactic empire as we expanded our explora-oh wait a minute. THIS GAME HAS NO CO-OP BECAUSE THE DEVELOPERS FUCKED IT ALL UP!

- Super Mario 3D World! ----> I Love how we do work together but still sometime get competitive. And YES! my voice cracked after the 1st day playing it with my brothers XD

- Mario Kart 8 ----> Trying to unlock the maps and stuff together is much funner than doing it alone. Especially when your trying to let a certain AI not win XD

- Hyrule Warriors ----> It was actually quite fun playing it with my 5 year old brother. We just keep telling each other where to go and stuff.

Does those MMORPGs and League of Legend count?????? If it does I would like to mention:
- Mabinogi ( Simple but quite fun battle style, but I do love how the "fantasy life" aspect of it blends sooo well!)
- Dragon Nest (BEST MMORPG GAMEPLAY/BATTLE STYLE I HAVE EVER PLAYED!!!!!!)

And that Ratchet and Clank game on my PS2 was quite fun!

Knew I was forgetting one, exclusively played co-op with this game's story mode.

Also beginning of this gen the only thing I played for months was NintendoLand and co-oped the hell out of TLoZ Battle Quest during that time.

@Rine: Arigato :)