Arkham City, without a doubt.
Either way, avoid Mass Effect 3 until it's down to like twenty or thirty bucks or something. If it didn't have the Mass Effect name on it, it would have been written off as another bland Gears of War clone. It's not that I hate the game or feel any animosity towards it, it's just bland.
At least Catherine isn't really a clone of anything.
Arkham seems like a obvious (but boringly safe) choice, no? Mass Effect 3 is enjoyable at very least though there's lots of things that annoy me about it... and Catherine is really interesting from a conceptual point of view but you might hate the gameplay so what I'm saying is...I DON'T KNOWHOHOHOHOoo...
Also it feels like ages since I've seen you Pessh. Where the Hell did all the people I follow from the past two years go to?
If you've played the first two ME's, than ME3. Catherine, although I haven't beat it, and it's not exactly my type of game, I enjoyed it quite a bit for the most part, but got a little bit annoyed at the puzzle levels at times, I'd recommend not taking those very seriously though 'cause it'll just make it worse and harder. I loved Arkham Asylum, but was severely disappointed in City, I just found a lot of it incredibly boring; the story, majority of the game play, and I really expected more out of the setting/atmosphere. I'd say ME3 if you've played the first two, and while I was disappointed in Arkham City, I'd still say get that over Catherine. Mass Effect 3 isn't perfect of course, it has a few bugs in it, the fetch-quest stuff is filler, and the whole reaper chasing you on the map is annoying.
Mass Effect 3.
Catherine was no doubt the most interesting, purely just because it's so different to anything else i've played. Although you will pull your hair out in frustration at the block puzzles!
Mass Effect series had me most invested time/ money wise.
However no one beats the Bat....and personally I had the most fun playing through Arkham City than any other game on your list, so yeah...get that!
Arkham City was a disappointment for me in a lot of ways despite still being a very good game so if you have a ME2 savefile then it's a no brainer - ME3 is still a very good game, just doesn't play as well as the previous iterations did and despite all their promises it is even more streamlined towards action than before.
Don't get Arkham City, as the GOTY edition is coming... soonish? September for the UK I think anywhoo, because, y'know, European delays. >_> It's easy to find it priced at around only £25 on consoles, too.
EDIT: Oh, right, in fact it should already be released in the US...
im going to say buy mass effect 3, its a pretty damn good game dispite the ending controversy. plus they fixed that with a free dlc, so thats not even an issue anymore.
arkham city is a great game, but i beat it in a weekend and its been sitting on my shelf ever since. so just rent it, the catwomen stuff sucked anyways
I vote ME3, if you like story and character interaction it is better than the other two in your list though Catherine has some neat moments. If you played 1-2 it is a no brainer even. If you don't like "RPG" elements though and only want a game you can play and have fun with go with City even though I consider it to be another one of those horribly over rated games that you are better off just giving a rent because you can see all there is to see in one weekend.
I'm sure that no one cares, but I went with Arkham City, enjoyed it much more than the first bar all the stupid guns. Just picked up ME3 too which I'm looking forward to once I get around to doing a final ME2 save, and I'll probably end up Catherine too once I'm in the mood for something different. Thanks for all the responses, you were all very helpful.
@eroticfishcake: Yep first time I've posted in forever, kinda just stopped visiting the forums and playing games =/