I've never been to Alton Towers, but I think that Nemesis looks like the best ride there. Inverts provide such great forces, and I've heard Nemesis is no exception, and the extensive themeing put into it is phenominal.
Second would be Oblivion. It looks like the best adrenaline pumper in the whole park, and if I went to Alton, it would be my first Dive Machine. I bet looking down into the darkness is pretty scary on your first time.
Third (as far as I'm going to go) would have to be Rita. She (or he if she is a cross dresser) looks a bit boring compared to other accerelators, but Rita is quite unique and has a launch (which is always fun), which is why I picked her as #3.
Nemesis is definitely my favorite, that coaster is amazing. My second favorite would be Rita, it's not the best accelerator ever, but it's still good and my third favorite is Duel (which isn't in your poll) just because it's a fun ride.
Well, im gonna break the mould and go for 'Air'. Fair enough, the themeing and the overall build up are nothing compaired to Nemesis, but when i had the choice for a second ride between the two, Air won my choice, as i find it a much mroe enjoyable experience
It's close between R-QoS and Oblivion. I like them both for different reasons, and it's very hard to choose between them. Rita is my No.1 coaster, but I always add "and Oblivion follows very closely", because I can't bear to think that one would get a mention and the other wouldn't!
Nemesis for me, though it is pretty close. Air is really good, but loses it's novelty after a while, and feels a bit slow. Oblivion, although is a one trick pony, just get more intense everytime I ride it. Rita is a good ride, I just hate the theming, and it is a little boring. I really like Spinball whizzer and Hex as well. And I think the rapids are underated.
5.Duel - Although I usually stay away from haunted houses due to my nervous disposition, I will ride this because the LED shooting is such a catchy concept.
4.Air - A great ride (It's B+M so it must be good). It may not be forceful or thrilling but it's nice and calm which makes it very good to ride.
3.Rita QoS - This has started my want to ride more launched coasters because the launch really takes it out of you.
2.Oblivion - It's not as scary as other people make it seem for me. I still love he drop which is brilliant. Even though a one-trick-pony, it's a good trick.
1.Nemesis - Do I have to say why? Relentless forces throughout the ride. After riding the back row at the live, I know this is my favourite. The theming is brilliant. I just need a replica copy to put in the field opposite my house* and I'll be in heaven.
* But let's face it, that's never going to happen.