I prefer at least 60fps.
I remember when we got Sonic Adventure for the Dreamcast for the first time, the game had the option for either 50hz or 60hz. At first our TV couldn't play 60hz, but when we got a TV that could, it almost looked like the game was somewhat 3Dish, as in watching a movie with polarized glasses.
I would definitely chosen 60 Hz over 50 Hz,
I've played Sonic in 50 Hz and I hate how he feels not as fast and how the music turned out,
compared to how I play Sonic in 30 FPS on handheld, Sonic still feel fast and the music is same thing.
FPS is how many frames our console is producing or drawing, while the refresh rate is how many times the tv/monitor is refreshing the image on the screen.
The difference in Hz (refresh rate) is bigger than in FPS (frame rate).