Well Baldur's gate is quite possibly my favourite RPG of all time, not just of the isometric type. So I highly suggest that, but you're already set on that it seems, so I'll suggest Baldur's gate 1, as it starts the story that the sequel continues, and then the Expansion pack to BG2, Throne of Bhaal sorta finishes it. But BG2 is probably the best and if you play that first there is no point going back to the first as it spoils most of the mind fuckery in the opening scene.
I would also suggest Fallout 1 and 2. Which are nowhere near as good as Fallout 3, but very good for what they are, especially the second (its a lot easier).