I used to be an anime nerd which I had gratefully grown out of thanks to my short attention span. So I seen quite a few.
Naruto - This is one of the first I watched. I liked it at first but after that story arc with the bridge, it slowly and gradually rotted to a pathetic lump of crap. The spin-offs didn't help, although I thought the idiot brothers were the BEST characters in the series. That says something about how great the characters are. Some of the flashbacks were really pointless, especially the one during Naruto and Sasuke fight in that waterfall place. Yup you read right, DURING. They have to hold back the best fight in the series so far with a pointless flashback that was thought up at the last minute. The fight scenes were cool but apart from that I really couldn't give a shit about the characters, even during my early teenage years as an anime nerd, it was too pathetic.
Bleach - It started out pretty good but like Naruto, it went downhill after the first arc (the one where Rukia is sentenced to death, although she's already dead...). The fight scenes were the only good bits about the whole series really. The episodes dragged on and on and on and on at a completely unnecessary pace and the story is a load of shit. Probably the worst I've ever heard. Oh well, at least the characters were better than Naruto's.
Full Metal Alchemist - From what I remember this is probably the first anime I've watched and enjoyed it a lot. It was dark, had some good plot twists but I don't remember much about it. I might watch it again one day.
P.S. The movie sucks.
Elfen Lied - Very dark and moody and lots of yummy gore. The amount of nudity was completely unnecessary though. That's what hentai is for. The story is good and the way the characters were mixed into it was good. It did end a bit weirdly and there really should be a second series.
Lucky Star - Got boring after about 18 episodes. The random chitchatter of a bunch of random girls is only amusing for a while.
One Piece - It's a very entertaining show with good and likeable characters and story although annoying in some ways. Like how people get life threatening injuries and get blasted by giant cannons and get beaten up shitless all the time and never die. Repeating fucking flashbacks for the upteenth time or having such a slow pace that if a Japanese snail made this, the episodes would be cut by half and that's still fucking slow. Hence caused me to get sick of it.
Their fanservice is shit too. I wanted to see Robin in her sexy cowgirl suit again dammit! Err... *cough* *cough*
The Melancholy of Haruhi Suzimiya - The story was interesting and the show was entertaining and that's all I can say. Although it was really annoying trying to find the episodes in the right order.
Tengen Toppa Gurren Lagann - This show was so crap... Kamina was a great character and it had the biggest anime slut ever (and she is like 14 or something) but really, the show was pretty damn boring.
Utawarerumono - I watched a few episodes of this, was really boring.
Cowboy Bebop - watched one episode of this and for some reason never watched it again.
Full Metal Panic - I've watched a few episodes of this but I just don't remember it. Probably didn't impress then I suppose.
Oh yeah and there was Code Geass, I think I got bored of that quite quickly.
There were also some others that I forget the names of, one was called "something" violet, there was a stupid robot one and some guy that turned into a demon. I think that one was DNAngel.