I can't stand a game that doesn't take into account positioning. Unsuprisingly, the many permutations of the LMBS throught the Tales series has been a favourite, as well as Tactics Ogre and other TRPGS. Another system I thought was great was the Mega Man Battle Network battle system.
Golden Sun somehow got a pass, as does Pokemon. though. Hmm.
@fredchuckdave: You might be interested to know they've rearranged pretty much the entire soundtrack in the latest update; no longer does the game "try and put you to sleep," as I believe you've said in the past.
And if GGG keeps up the ladder resets and has zany modifiers for some of its ladder challenges I can see people playing it for a long, long time.