I've been building models most of my life, and I've built probably all levels of quality at one time or another. I did take some time away from the hobby during high school and college, but once I got my life on track, I re-discovered the hobby and found that kit quality had improved dramatically from when I left in the early '80s.
I've done some real fine Tamiya, Hasegawa and Accurate Miniatures kits, but for me my favorite comes down to childhood memories - Monogram kits from the '70s. I've re-built most of them since rejoining the hobby, and my favorite would be the 1/48 P-40B and the 1/48 B-17G. There was always a decent level of detail in these kits, and I always loved the movable features that most of these kits had. Loved the folding wings of the US Navy fighters and the retractable undercarriage that most of the se kits had.