I've only made a few 'endless' games myself. There's a certain appeal to them. Minecraft Beta, the long drive, Yumme Nikki, tower defense games. Games that you can play forever and never really quit.
but there is also a huge difference in design philosophy there that doesn't apply so well to games with more of a story focus, which is where I usually work. Both ideas are great, just different types of feeling you get from them.