For me Super Mario Galaxy 2 is about the perfect length for a single player game, it's not too short that you feel underwhelmed, and not too long that it gets boring, but if you do find yourself wanting more after the credits roll, the content is there.
I suppose though as long as you keep it fresh a game could be as long as it wants, to me Red Dead only felt so long because it slowed down and the missions got repetative around Mexico. Dark Souls was probably about the same length as RDR but it didn't feel like it because it kept you on your toes the whole time.
On another note, i got Epic Mickey 3DS for xmas and beat it the same day, really fun game but felt ridiculously short, i think the length of a game should be a factor in it's price. It hardly seems fair that a game like epic mickey which lasted a few hours costs the same amount of money as little big planet 2.
I suppose though as long as you keep it fresh a game could be as long as it wants, to me Red Dead only felt so long because it slowed down and the missions got repetative around Mexico. Dark Souls was probably about the same length as RDR but it didn't feel like it because it kept you on your toes the whole time.
On another note, i got Epic Mickey 3DS for xmas and beat it the same day, really fun game but felt ridiculously short, i think the length of a game should be a factor in it's price. It hardly seems fair that a game like epic mickey which lasted a few hours costs the same amount of money as little big planet 2.