Final Fantasy V. Yes, the class system takes some work, but (iirc) you're eased into it; the story overall doesn't take itself all that seriously. I would've said VI instead, but between the Esper-based spell-learning system (which can easily be skipped, of course) and Gau's Rages, plus the bugginess of most versions, I can't quite recommend it as the 1st game.

...to my surprise, most of the other games that come to mind are either just SLIGHTLY too complicated and/or eyebrow-raising (SMT: Digital Devil Saga), not menu-based for the character you directly control (Tales of Symphonia), or were also made by Squaresoft (FF4,9,10; Chrono Trigger, Threads of Fate[aka Dewprism]). :/