Retinasizer does.

I have a bone to pick with certain developers on the iPhone.

To be honest, post June 24th, 2010, no one has any excuse to make a game that doesn't support the Retina Display. None!

If you are a developer who has a AAA title that you update periodically (looking at you, Capcom, SF4?!), you have no excuse. Why do you want your games to look bad on the new display that you know everyone else will be using?

We have moved on. We have since doubled our display resolution from 480x320, to 960x640.

This means that games fitted for the older resolution are being blown up for the newer display, with a disgusting pinch of edge smoothing for good measure.
I have personally refused to pay $9.99 for Sonic 4 in the App Store until they fix this. Many games, like Grand Theft Auto: Chinatown Wars , also share the same fate (the latter being a slap in the face because R* took the time to upconvert it for the iPad)

But in the interim, we have jailbreaks. A free update through Cydia called Retinasizer by Sticktron does exactly what Sega and those other companies refuse to do in the form of a tweak that forces game content to run at the iPhone 4's higher resolution. It doesn't work with every game yet and is still very rough around the edges, but there's no denying that if someone can come up with a general purpose tweak and force it, then these companies are just sleeping on purpose.

If you have a (jailbroken) iPhone, I implore you to check it out, as the difference really is night..

..and day.