Interesting--I talked with the GF about it again tonight and she brought up basically the same points that you did. For me however, I find that first-person perspective in RPGs often discourages me from being really immersed in the game, as it leaves little to the imagination, puts everything that feels 'wrong' (using Skyrim as an example: the floaty combat and NPC interaction) up close and personal, and just generally doesn't do my suspension of disbelief any favors. (Of course, there are some exceptions--I generally have a good time with first-person games where atmosphere is key.) Having played tabletop RPGs growing up and having had experience with them before I really got into computer role-playing might have something to do with this--playing a good tabletop game with a good group of storytellers is about as immersive as things get for me, akin to reading an excellent novel, albeit it one I can interact with. (Perhaps like a dream?) Isometric perspectives reinforce the idea in my mind that what I'm really playing is, to some degree, a simulator of a tabletop game, and if the game mechanics are solid and the writing is good, my imagination takes care of the rest. For me, that element of imagination is missing from a lot of modern RPGs, and I personally find its absence or near-absence to be detrimental. I've walked the streets of Baldur's Gate, but I've only played a game that took place in a fictional country called Skyrim.
On the note of 2D vs. 3D--I don't see your argument. Not every game is better in 3D. Technically maybe, but aesthetically no (granted, this is an entirely subjective point). Nevermind the practical angle of the game development process and the differences in cost, staff time, and staff expertise in making a 2D game vs. a 3D one.