There was always something really earnest and likeable about Data for me. I know they went to cliché places a lot of the time with his really wanting to be human and failing spectacularly at it, but that really worked for me when I started watching as a teenager, the fact that he was so brilliant but had no idea how to relate to the people around him and still ended up being more human than they were sometimes. (So speaks the genius kid who got held to her age level in school instead of advanced according to what she could actually do).

I hated, hated, hated how they dealt with the Data subplots in movies seven, nine, and ten-- I've only watched them once each and have no desire to again-- but on the other hand I did love the stuff with him initiating dream subroutines on the show, and the time Q allowed him to experience laughter before he found out about the emotion chip, and the episode where Picard was stuck on the Enterprise with terrorists during a baryon sweep while Data engaged in a small-talk marathon with the station commander that everybody else hated talking to, and the bit in movie eight where (IIRC) the borg Queen tempted him with a closer approximation of humanity than he could reach on his own and he was so tempted but didn't really give in, and so on.