Done two of them, and quite enjoyed both of them, probably because I've only had one visit each.
1. Alton Towers - Love the setting. There's some really nice areas including places that don't have any rides, like the open field or the gardens. The whole park honestly felt special to me. Not the best ride selection, but I like Air and Oblivion, and Nemesis is amazing. Could honestly ride Nemesis all day.
2. Thorpe Park - Feels like a Six Flags park, but I actually left the park feeling pretty good, whereas I've had times where I leave a Six Flags park unsatisfied. I had 4 hours at the park and had a pretty decent time, with rerides on the good stuff and queues that weren't bad. Stealth, Inferno, and Swarm are all great. Colossus and Saw are fine but I'd ride them again if I ever return.
Chess does boast the best spinning coaster in the UK and the best suspended coaster too. That's two reasons. Alton Towers is very well coaster orientated and miles better than Chessi with choice of extreme rides and I'm happy to concede that but 'WOA' does have an unique ambience all of its own.
For just coasters Alton towers easily, But as an all round park Yea Chessington is my Favourite. When i go to Alton its all about coasters and Hex but at Chessington i find there is much more verity. While there has been updates to classic rides which are not as good as the originals they keep them going, DF and Vampire are great and don't get enough love and the zoo is always interesting to walk around.
Nemesis is still my favourite invert but all the outer coasters at Alton are either megh or i have got to go on a better versions of them so they do not hold up well, Chessington however still has my favourite suspended and spinning coaster. I also went here much more growing up so i have much more nostalgia from this park.
I've been saving this one til I competed the set. Was it worth it? No.
1) Heide Park - Nice place to be, well run and a good selection of rides, many of which are stand outs for what they are. Except Colossos, which is by far the worst, but still worth a few goes.
2) Alton Towers - Should be the best by now, but Wicker Man blew it and I've just grown so tired of the place. The lineup is nice and varied and they have 2 of Merlin's best (Nemesis, Hex), though I never really found anything joyously rerideable here even in its heyday. On quiet days now, I get bored and leave early. On busy days I get pissed off and leave early.
Sure, this may well apply to all of these parks if you went enough times, but I don't feel like I've overdone Alton to be honest. It just never feels worth the effort once you're in it.
3) Thorpe Park - I do genuinely like a lot of the rides here and I'd still want to go regularly just because it's there and fun, but haven't had the motivation any more with latest changes in pricing, passes, operations (and investments).
4) Gardaland - It was nice enough, but the rides leave a lot to be desired.
5) Chessington - Don't like what they've done to the place, can't remember the last time I went and nothing has been done since to make me want to return.
6) Legoland Billund - The standout Legoland with a single noteworthy and unique attraction.
7) The other Legolands - Overpriced and copy paste. Just cred stops to me now that I've since started skipping completely.
Windsor has a certain charm I guess but don't care, got the creds (wait, are they getting a new one?)