I would say Metal Gear Solid since it has yet to disappoint, oh and just to clarify to some people Metal Gear Rising isnt apart of this since you only said MGS, i say this cause i know someone will bring it up.
3DS Friendcode: 3566-2243-3100 PSN: The GraveJoker
If we're taking in account spin-off titles too then I think Final Fantasy slaughters Metal Gear Solid but I'm still a big fan of the stealth genre (is that a genre?) and I really enjoyed Metal Gear Acid, so both series are a lot of fun to play.
Check out my friend's gaming blog! - http://gameternity.wordpress.com/
i hate when people say things like this. he aint asking you to compare how similar the games are. hes asking which is better = which you think is better. this is me saying i like the avengers better then titanic and you going they're completely different genres. i dont give a f*** if theyre different genres, i like the avengers better