The example of this closest to my heart has always been Pharaoh, an amazing game from 2000, which looks a huge amount better than it's spiritual successor, released in 2004, Immortal Cities: Children of the Nile.
2D ages better too. So many PSOne/N64 games have aged badly in terms of looks (especially now with HDTVs) but SNES and sprite-based PSOne games still hold up.
In fact, it can be annoying. I've been playing Europa Universalis IV, and I quite enjoy the game, but as an owner of an older laptop with good specs but a weak graphics card (quite common in "business class"), I really wish it had a 2D mode.
A good 3D remake would use the same models, which really are beautiful. But in 3D you could experience them with so much more clarity, from any angle and at any zoom. It just makes the experience so much more immersive.
I realize that this is just my personal taste... I love 3D movies too!
http://image.buildinggame.net/screenshot-cleopatra-game-buil... http://cf.shacknews.com/shack_images/sshots/immortalcities/1...