I dislike the term 'girlfriend co-op', but whatever, it describes what I'm looking for :)

Edit for clarity: We have two PCs, mine is awesome, her's isn't.

In a week I'll be moving in with my girlfriend, and she asked me if we can't start playing games together again. We played a lot (like 40 hours) of Civ V together this summer, hot seat, which was fun, but not enitrely enjoyable since we did it on her aging PC. That's kind of why we stopped as well. The platform is PC, only, and preferably games that can be played with keyboard and mouse since she doesn't have a controller (yet). Her PCs specs are 9800GT, C2D something and 2 GB of RAM. She likes action the most, and got a bit confused by Civ sometimes since it's requires you to make like a billion decisions and to keep track of tons of things, as she hasn't played tons before.

Games I've thought of:

Left 4 Dead 2 (thank you L4D2-proposal guy) - bought it for her today as it's the daily deal

WoW - we played some, stopped mainly due to me getting bored (I have over 400 days in-game time played, I've seen most of it)

Saints Row 3 - which is probably impossible due to her PC..?

Dungeon Defenders - is this game good in co-op? I've heard it's supposed to be awesome. I guess we could give the demo a shot.

Before anyone says Borderlands, I think it's sort of boring :( Yes. I'm a bad person etc.

Terraria or Portal series maybe? I can think of a lot of shooters but I don't know whether they'd be to her taste or yours.

Shooters are fine, we both like shooters. Just not Borderlands, and as long as it's not MP (as in BF3). Been thinking of Portal yes, and Terraria you say? Will take a look, thanks.

Are you playing on the same PC? Or will you have two now?

Anyway before that how about Trine?

Or some free to play MMO to see if you like it?

Can't go wrong with You Don't Know Jack.

Dungeon Defenders is pretty fun. Try it out.

Sodomy.

Single computer? hmm.. 
 
Lara Croft & The Guardian of Light is the best couch co-op game I've played in years, and it ran on my old 8600GT PC well, so that is absolutely my pick. You don't just run next to each other shooting, you actually play co-operatively and help each other out, it's great fun. 
 
But, how can you play co-op on the same machine (her PC) if there are no controllers? 

I guess I was unclear - no, there will be two PCs, hence me posting the lower PCs specs and buying L4D2 for her. FOREVER LAN PARTY YALL!!!!!!!

@endaround: Will check out Trine 2 soon anyway so, but isnt that very demanding? I remember Trine 1 being very unoptimized.

@Sjupp: Will do!

@Th3_James: One of our favorite games!

@AhmadMetallic: Will check out Lara.

Team fortress 2 - free (would have to play with other ppl tho, dunno if thats what youre looking for)

battlefield 2 - still a good game (again, MP more than co op)

look out for Torchlight 2, it's not out yet (co-op)

Resident evil 5 if you could get it to work on her machine (coop)

Killing Floor (MP co-op)

EDIT: out of the ones that other people mentioned, Terraria was the most fun for me along with Dungeon Defenders.

ALSO, Magicka (or something like that, they spell it werid) is great.

@zels: Dungeon Defenders is looking like a sure thing.

Just ultra bummed out I missed the 75% sale.

Terraria is great for co-op play. Also, you only have to wait a few more months (hopefully) for Diablo 3.

play dead island with her, girls seem to like zombie games for some reason.

Girlfriends are meant for fornication and sandwiches, not vidya games!

@Poost: Yeah we already tried the beta, apparently she used to play D2 with her dad. I never ever played a hack n slash game so that could be quite good, as I won't be that much ahead. Going to take a look at Terraria, even though I find Minecraft and it's spawn very boring. Terraria seem to be more game though.

@Marz: Played through it once with friends, never ever doing that again. But yeah, girls like to kill some zambies.

Im just here to tell you to play Dungeon Defenders and Guardian of Light again. I played the latter with my ex and she quite enjoyed it, DD I've been playing with a bunch of friends and it's a blast. Magicka is also not a bad choice but its a bit more niche, depends on how many games your girlfriend plays/her general skill level.

@Ertard said:

@zels: Dungeon Defenders is looking like a sure thing.

Just ultra bummed out I missed the 75% sale.

With xmas sales coming up this week, I'd say its a pretty safe bet that you'll see it cheap again.

@NyxFe: Thanks for reminding me, will keep a look out.

Might as well try Alien Swarm, I really enjoyed that co-op when it came out (man, that game could've really been something... but that's another topic), and it's free so that's nice. Portal 2 should work. Renegade Ops might not run too well, but hey, a suggestion. Dawn of War 2 has co-op campaign and "The Last Stand" mode is pretty fun if you're less into the RTS-ness.

I'd second (third?) Portal 2. It's running on the source engine, which is really easy on aging pc's.

Also, Magicka is a whole lot of fun for pretty cheap.

I'm glad people have mentioned Terraria, as I'm throwing my support behind it. It was gifted to me about two weeks ago. I didn't expect much from it. The game currently controls my life; I've dumped around 40 hours into it.

And, not to generalize, but when I think of games that girls might like to play, Terraria is pretty high on the list. It's not terribly violent, there's a Sims-ish component in that you make homes for people, there's a big emphasis on exploration, and there's the ever-present carrot-on-a-stick in the form of insatiable loot lust. There is no leveling system, so you two couldn't ever work too far ahead one another. Your ability is determined strictly by your gear, which you make yourself 90% of the time. After playing the game 40 hours, I had a friend join the game yesterday. I gave him extra gear I had and now he's practically on the same level as me. It's a nice system.

Maybe try SWtOR? Pre-orderers can start playing in a few days, and it looks like a WoW that you won't get bored with as quick because you haven't seen it before.

Also Diablo 3 and Torchlight 2 should be on your radar.

Infinity Engine games are co-op, so perhaps some Baldur's Gate for a few hundred hours?

@mikeeegeee: Will try it if it comes on a sale. She loves extreme violence though.

@Red: I might try it. Maybe we could. It's just that I'm pretty hardcore about my MMOs, and I'm not feeling SWTOR at all. It looks like absolute shit to me (raid videos all look AWFUL). But I've been meaning to play it for the story.

@endaround: Man, I tried to play BG2 recently and bought it off GOG, but I couldn't deal. Too complex and too old.

Since no one's mentioned them yet, I'll go ahead and suggest Minecraft and Neverwinter Nights.

Also, Amnesia is a co-op game for me. I *can't* play that game alone.

Age of Empires II . - you can set up teams and if shes on your team you can protect her as much as she needs.

Pretty much all I can get my gf to play with me is Portal 2, Left 4 Dead, iOS games, and DS games.