Ah! I've played Adventure Quest but not AQW! AQ was singleplayer and like AQW was to you, AQ was a part of my childhood, too. I remember actually deciding my fighting strategy with each monster based on their stats / weakness against certain kind of magic, and buying pets and stuff from NPCs. The graphics were so simple and cartoonish. It was a quite interesting game to play. :)

Also not too long ago Adventure Quest 3D came out as a MMORPG on Steam. Have you played it? I did a while when it was still in Open Beta (around 10h) but haven't picked it up later.