Well, I'll post all the games I've beaten when I was amazed that I beat them in that short of time:
Super Mario Bros. 3: 11 minutes and 32 seconds
Final Fantasy X: 23 hours and 9 minutes (23 hours is QUITE fast for this loooong RPG. Most people I've looked at have beaten it in either 32 hours to 41 hours. The HIGHEST I've ever seen is 68 hours. But 23 hours is quite good)
Legact of Kain: Defiance - One Day
and
Super Mario 64 in 5 days (Yeah, I was amazed. This game usually took me like 12 days, but the second time I beat it it was 5, then the third time was 14...O_o)