So I primarily play on PS3, my sister gave me her old 360 over a year ago and so far I have a grand total of 4 games for it so I was hoping you duders could help me find some good games to try?
I'm including 'exclusive' games that are also available on PC.

I'm not really fussy when it comes to genre, WRPGs are my favourite & I'm not overly keen on shooters unless they have a cool story but I'm open to pretty much all suggestions. I'm not interested games that rely heavily on online multiplayer though.

I already have The Witcher 2, Fable Anniversary, Fable 2 and Viva Pinata

So far I'm thinking of getting Alan Wake, Risen and Fable 3

Alan Wake rules. Play that. 5 out of 5. Don't expect a shooter, expect a cool atmosphere/story that feels all twin peeks-y and is dope.

Honestly Microsoft really didn't do as good as Sony did with exclusives. My personal opinion would be Forza 4 (really fun with the Microsoft speed wheel or any other wheel). They really relied to heavy on shooter's which usually the online was the best part.

Gears of War series had its moments, feels like a big budget summer movie, and fun Co op mode if you can find someone to play with.

Project Gotham Racing 3 or 4 another fun racer. Alan Wake was good and had me drawn into the story. The Geometry war games where fun but you can get them probably cheaper on pc, fun duel stick shooter.

But really it's pretty disappointing because 3rd party titles really did sell that machine, Microsoft imo is the one 1st party game system maker that really doesn't do enough exclusives, if the ps3 wasn't so much money at launch I don't think Microsoft would have did as good as it did last gen. They really did become lazy with 1st party exclusives.

Alan Wake is great, def play that one. Forza Horizon is fantastic. Not a race game guy, but Horizon is laid back, open world driving fun. Also, I put a ton of time into World of Tanks. Fun and free.

Crackdown. Yes, play Crackdown.

Banjo Kazooie: Nuts & Bolts is also an underrated, exclusive gem!

Alan Wake is awesome. Most people considered Fable III a disappointment but somehow I enjoyed it more than Fable II. (Though, I'm hesitant to call it a great game or anything)

Kameo: Elements of Power was awesome. Among my top 5 favorite RARE games for sure.

Shadow Complex if you like Metroidvania games.

Crackdown is fun, though I think that's best played with friends in co-op. (It doesn't have to be, but that's when it's the most fun)

Bangai-O HD: Missile Fury I'll continue to be the one person who recommends this game.

Dust: An Elysian Tail is pretty good, though I never beat it.

Halo ODST and Reach are fantastic. I'm not that big a fan of the main series.

I'd say Fable 3. Fable is a great franchise, if you approach it looking for a funny and whimsical fantasy rpg filled with british humour, and Fable 3 is a good example of that, also with a good story, good locales, and also one great DLC - Traitor's Keep.

Alan Wake is great. A lesser great but still interesting game is the indie Alan Wake: American Nightmare.

As indies you could also check out State of Decay.

If you like jrpgs you have also Lost Odyssey, with a turn based battle system, or Infinite Undiscovery with a active battle system. Both are good games.

Brilliant suggestions so far, thanks!
Yeah the PS3 certainly has the advantage when it comes to first party, its one of the main reasons I chose it over a 360 (I jumped in to last gen kinda late)

I've been thinking about some of the Halo games but wasn't sure which (if any) were worth getting just for single player campaign :/ Same thing with Gears of War really.

Regarding Fable 3, I've played Fable 2 and enjoyed it (though its not one of my favourite rpgs) so I think I'll give it a chance since I can get it really cheap.

I was thinking about Lost Odyssey before actually, it looks almost like a 'good' final fantasy aha so I think I'll get that if I can find it fairly cheap. I'd completely forgotten about Banjo Kazooie nuts&bolts - think I have to get that purely because, well, Banjo Kazooie :P

Not heard of a few of the others so I'll certainly look in to them :)