Fischer is probably #1, and if not him then Capablanca. Or did you mean active GMs?
Highest win % from a GM

pretty sure there was a similar thread recently where someone listed all the stats, but i can't seem to remember it's name.

LOL what!?
It was me who gave the percentages and it was YOU who started the thread.
lol oh yeah how did I forget

In 1972 (before the WCH match was held) I read that Fischer's winning percentage with Black (72% I think) was higher than Spassky's winning percentage as White. (60-something) BUT Bobby also had a very "high" losing percentage among World Champions, 10% or maybe even 12% if I recall correctly. Capablanca's lost 35 "serious" (international tnmts and matches) games out of about 700 in his life giving him the lowest losing percentage (5) of any official WCH.
http://www.chessmaniac.com/index.php/2012/11/30/world-chess-champions/ http://moscow2012.fide.com/en/history
This site is great if you have too much time on your hands and want to check out the greatest players in history by their 1,2,3,5,10, 15 and/or 20 years of peak performance http://www.chessmetrics.com/cm/CM2/PeakList.asp

For World Chess Champions it's 1. Capablanca 2.Alekhine 3.Fischer in terms of overall % scored. Don't know about winning in particular.
Here is the ranked list of top chess grandmasters based on their all-time win rates:
- Mikhail Tal – 65.20%
- Emanuel Lasker – 61.71%
- Garry Kasparov – 55.90%
- Bobby Fischer – 54.33%
- José Raúl Capablanca – 53.54%
- Alexander Alekhine – 53.31%
- Magnus Carlsen – 53.25%
- Anatoly Karpov – 52.63%
- Vladimir Kramnik – 52.33%
- Mikhail Botvinnik – 52.21%
- Viswanathan Anand – 49.85%
Which GM has the highest win %