Recently there seems to be a trend of retro games intentionally making games look 20 years old, but then there are those that turn this on it's head and take those 2D art and make awesome looking modern games out of it, by adding 3D lightning and effects.
Some cool examples (closed source):
http://www.robotloveskitty.com/LoD/
http://www.wingsofstnazaire.com/index.html (check the vid: http://www.youtube.com/watch?v=lTcHSGn2h1s the enemies are 2D sprites!)
And there is also this cool advanced open source 2D engine (no linux port sadly):
http://ethanonengine.com/
But basically and OpenGL engine will do, and many 2D engines are OpenGL powered these days.
So besides looking mighty cool, this could be an awesome way of upgrading the graphics of rather old looking 2D open-source games (which is often the main complaint by non-enthusiasts).
For example "pimping" Abuse (http://abuse.zoy.org/) like that would be mighty cool, or maybe the Ur-Quan masters etc.