From the top of my head...
Over-rated:
RITA - I'm not sure if it's because the coaster is in Alton Towers, but it's so well-praised, especially by non-enthusiasts. RITA just isn't a
good rollercoaster, in fact I think it's one of the
worst launch coasters I've encountered. The launch is ok, but everything else is uninspired. The layout is as dull as a Big Apple, the air-time isn't that good, the theme is lame, the queue-line takes the piss, the name is lame, the reliability is bad, it's rough and to me it's put Alton Towers to shame. Nemesis, Oblivion and AIR are all top-class rollercoasters, RITA could've been a
much better rollercoaster, even if it had a tunnel or more extensive theming, it would do it a good job.
Kraken - This is another coaster that could easily be a lot better, but is flawed by having such a recognizable layout and being sluggishly forceless. After being on Dragon Khan (which really impressed me), I couldn't help but hesitate to compare the two coasters. The layouts are pretty much identical, but Kraken felt a lot more drawn-out and elegant rather than Dragon Khan being tight and intense, in fact I couldn't really feel anything on Kraken. Kraken is smoother than Dragon Khan though, but this just made it feel sluggish to me, rather than being shaken up and a lot more wilder on Khan. The difference between the two coasters is huge, Kraken just lacks personality, whilst the theming is beautiful, for the mass of the coaster it just felt tame and rather boring.
Under-rated:
Stampida - I love this wooden coaster! And you can have some outstanding rides at night if you choose the right place to sit (back-left of red train). Sure it's rough, but it wouldn't be a woodie if it was glass-smooth. Just slouch your bum forward when the bar is being pushed down, you can have quite a gap, which allows for some seriously insane air-time! It's a shame this gets over-looked so much because of it's brutal rattling and poor trains, the layout is fantastic!
SAW: The Ride - I don't know why this gets so much hate on here, it's the best addition at Thorpe since Nemesis: Inferno. It's far from rough, if a little jerky, and the effort put into this coaster is over-looked. From the indoor queue theming, to the cheeky addition of an air-time hill (and a good one at that), it's transformed a simple Euro-Fighter into a world-class coaster. Euro-Fighters in general are under-rated.
I'm sure there's more, but those stand out the most for me.
