Keihas was spreading at least a bit of misinformation. Some other commenter pointed to a WWII mod for Quake2 as an example of a game that had iron sights, but you can do much better with actual UT mods.
IIRC The Third Reich, a WWII mod for UT, had most of the features Keihas mentioned (iron sights, bullet penetration and ballistics, free aim) in its 1.2 release in 2002. The Third Reich (TTR) did not have controlled breathing or weapon collision, but these features have generated some debate within the INF community and in any case are somewhat negligible (e.g. in the sense that you may need to spend a day to get used to not hitting your weapon against a surface). INF does probably have superior, fluid free-aim implement and I'll be impressed if another game could pull it off that well.
I haven't played RO since the ut2k4 version, but the game wasn't that fun then. I can't remember all the details, but for one the level design was not particularly good. If TTR took anything from INF, it was AngelHeart's levels, but almost all the maps in TTR were superb, whereas no RO map really strikes me as memorable. Since the gameplay was essentially "multiple TAS" for the most part, having good maps were crucial. I only played RO because the TTR community was slowly dying then. Eventually my interests shifted towards modern warfare, so INF was a natural choice.
