A writer from AnandTech got a look at Epic Games' Unreal Engine 3 working on the newest iPod Touch. It's an impressive feat even if there are some asterisks.
The Unreal Engine 3 will only run on third-generation iPod Touches and the iPhone 3GS, and the demo being shown is not a fully-operable game, just a stripped-down version of Unreal Tournament.
Some elaboration from AnandTech from their meeting with Epic Games V.P. Mark Rein:
Epic isn't announcing any sort of iPhone engine licenses nor are they entering the iPhone game market. Porting UE3 to the iPhone is simply one of many projects being worked on inside a newer, more svelte and innovative Epic Games (wait till you see what's next...)... Mark said they planned to make this available to licensees at some point in the near future.
And here's a thought experiment: How about a recent Epic hit ported to the iPhone?
...eventually it wouldn't be too far fetched to see a full port of Gears of War to something as small as an iPhone. NAND Flash capacities to support multiple 9GB games will be there in another few years, as will GPU horsepower.
According to the site, Rein said that Unreal Engine 3 support will be announced for "another mobile platform" at next month's CES, the biggest tech show of the year.