Hard choice for me between exploration and combat, but chose the former with questing a definite third. They're all pretty inter-related, as questing leads to exploring in many cases, and exploring almost always leads to combat, so its all part of the same ball of wax to me.

Still, combat is a very important facet of RPG's for me, as it's both enjoyable in itself and the framework that experience-based leveling is hung on, and so bolsters the other aspect I wanted to pick, character development. (Too many choices! Probably just as well 'consequences of one's actions' wasn't listed or I would have agonized over that as well.) I would say you couldn't have a successful RPG without any of these elements, for me , anyway.

Least important for me are puzzles and NPC interactions. I don't mind them when they're done well, but most times they're more of an annoyance or a cliche.