Games to play with your GF

Rocket League maybe?

Might be to expensive though, I don't know, I do wish you good luck and have fun when playing!

borderlands
broforce
castle crashers
dead island
l4d
lara croft and the guardian of light
lego
magicka
orcs must die
portal
resident evil
trine

¯\_(ツ)_/¯

I would recommend "golf with friends" and "ultimate chicken horse" they are both easy,cheap and fun. and maybe some fighting game you both don't know how to play.

I'd recommend these (Iplayed them with my gf):

Trine 2
Battleblock Theater
Monaco: Whats Yours Is Mine
Card Hunter
Ibb&Obb
Portal 2 Coop Test Chambers

perhaps she'll enjoy Torchlight 2?

Orcs Must Die 2, Ibb & Obb, Torchlight 2, Trine, Lovers in a Dangerous Space Time, etc... there were a lot of good suggestions in other threads, just search the forums and maybe you will find a good game :).

EDIT: Here, here, here and here for example.

Some games I played with my wife:

Terraria, Torchlight, Trine 2, Borderlands, Sniper Elite 2, Sanctum 2, Portal 2, Gauntlet, FEAR 3, 100% Orange Juice, Dungeon Defenders, Titan Quest, Lara Croft etc.

I do not recommend Castle Crashers, Battleblock Theater and Monaco, they're kind of hard.

She's not that good either, but we had fun playing these on easy difficulty ^^

Play sims together.

I think this game is good.
http://store.steampowered.com/app/6120/
You can select normal,even if your gf play not well,you also can complete it.

Gang Beasts
Transformice

If you wanna play together on 1 pc and just want some not too hard puzzles and bit of jump and run i can recommend the cave. Me and my girlfriend enjoyed it. But playing that game is rather relaxing and maybe not exciting enough to fill whole days ;)

Terraria..

Building a house with your GF, she will enjoy it.

My gf enjoys playing Terraria with me.

Don't starve together is indeed nice. Never Alone could also be nice (co-op one of you can be the fox). Nidhogg is fun, my partner and I play it together and then curse each other out ;). Lovers in a dangerous spacetime. And indeed, The Cave! Like that one too!

Divinity: Original Sin (the Enhanced Edition supports controllers)

If you're looking for an excuse to get into a fight and have makeup sex later, try Keep Talking and Nobody Explodes.

Portal 2, Serious Sam, Dead Island

dark soul 3? torchlight 2, magicka, boderlands

Try Dark Souls 3, it'll bring y'all closer together.

Kidding.

Try Terraria or Payday 2. Both are good :)

Streets of Rage Remake from http://www.soronline.net/sorr_downloads.htm
Double Dragon Neon
Colony from armorgames.com
CnCnet from https://cncnet.org/
If you both liked Hearthstone, try Infinity Wars, it's better
Heroes of Newerth
Dead Rising 2
Dungeon Defenders II
No More Room In Hell
Defiance
Loadout
Sven co-op
Strife

There's more games to play if you want to watch just her play, and look around for more. Can't afford a game, then yeah, ask for more worthy of playing free\flash game from me. You could always just watch and react to videos with her, you could record yourselves reacting to Honest Game Trailers and whatnot.

Lovers in a Dangerous Spacetime, Laura Croft and the Guardian of Light, all the LEGO games, Magicka, Towerfall, Spelunky (could be frustrating?)

depends on your girl. mine hates any shooters and "bangbang". we have played trine, magicka. now we're playing ibb and obb. great game! but the all-time favourite is bomberman on the wii.

but she also likes watching me play telltale (and similar) games and giving stupid comments. just like a let' play together. but she hates point&click adventures due to too much speaking and idling.

Here's an answer I gave on Quora for similar question:

Depends on the girl. I game far more than my boyfriend does so we don't play together often. But Lara Croft and the Guardian of Light was recommended and I'll second that, played with an ex and my current guy. It's fun. Trine is fun as well.

Used to play Dungeon Defenders and Terraria often with friends.

CS GO

I've played with my totally-not-a-gamer girlfriend Brothers - A Tale of Two Sons and she enjoyed it a lot. It is very short game though - you can complete it in 1 run cos it's only about 2 hours long.

Brothers - A Tale of Two Sons. It's really good. :)

i play jidden object games with my gf and some releases from telltale, if you want a more complex game tho think one that has a good story by both your standards and go for it