i stopped watching in season 10, i think. i cant remember now. the last i remember was april and jackson getting married. i think.
personally i loved seasons 1-3 but i think 2 was the best one. then i hated season 4 and i didnt like 5 either. i loved season 6 though. then from season 7 on it was just bad minus a few decent episodes. i hated all the recent couples in the later seasons, mark/lexie, callie/arizona jackson/april, owen/christina, BLECK. I couldnt really stomach watching anymore.
since I've stopped watching i heard derek died and christina left so it sounds utterly ridiculous to me, but someday i will go back and finish probably.
Favorite character is George 100%. Then Izzie, then Meredith. Then Jackson and Addison. I also love Callie and Christina is okay and I liked Derek and Mark too.
Favorite couple was george/izzie which i know i am in the minority for but whatever, i thought they were cute and treated each other so well. also loved mer/der of course but got a bit bored of them. and I'm in the minor for these as well but i loved owen/teddy and jackson/lexie as well. also mark/addison and alex/addison. oh and denny/izzy. and i crack ship meredith and alex and am still hoping they will hook up now that derek is dead.
best moment for me was 100% the season 2 finale with denny's death. holy crap those were some amazing episodes and scenes, i was bawling my eyes out when that happened. other memorable episodes were the bomb episode, the episode where derek died (i did watch that one episode), and the shooting episode.