Tbh I'm trying to answer for ages now lol, but can't find the good words, as it's really an endless debate & a question of personal perception. Basically i wanted to say 60fps looks far more real to me than 30fps, even if I totally agree to the fact 30fps looks fluid. Movies are 24fps, but movies are movies right? Videogames simulate reality. Kojima tweeted that because all the MGS ps3 remixes will run at 60fps, to enhance this perception of reality. I found a nice link on that matter btw, not a "scientific" one (just try "how many fps can see the human eye" on google), that's an interesting subject btw. It's raising basically this question, what are our physical limits in term of perception (higher resolutions like 1080p & way more, higher frequencies & so on).
http://www.boallen.com/fps-compare.html