However each game in this series has some problem in some other game this series doesn't have. This creates a paradox right don't play either game in the sit on the "top shelf" (which I'll explain some other time).
(In order of Canon)
Metal Gear Solid 3: Snake Eater is possibly the strongest metal gear game (at least that's what ever else says). However snake eater moves metal gear into larger outdoor environments that clash with controls that have not changed since metal gear solid (one). It's particularly jarring if you've played Metal Gear Solid 4. It's story is also excessively front-loaded and almost completely stops in the middle.
Metal Gear Solid: Portable Ops has a script that is ultimately fruitless (it takes Snake half the game to realize there's a Metal Gear involved). Portable Ops also has the worst controls of any metal gear game thanks to the PSP. If you own one you probably know what I'm talking about.
Metal Gear Solid: Peace Walker is not available as of this writing. Based on the demo I expect there to be some camera problems similar to portable ops.
Metal Gear lacks the near future science fiction aspects that I know and love from the series.
Metal Gear 2: Solid Snake is the same way
Metal Gear Solid has certain boss battles I'd rather not do mainly for tank and Vulcan Raven.
Metal Gear Solid 2: Sons of liberty gets a lot of undeserved flak for being stranger than its predecessor. Its script is infamously back-loaded with exposition with the second half of the game having little to no game play as well as having some poor dialogue (Though some of it is pretty funny). also what few boss battles as none of them are that enjoyable.
Metal Gear Solid 4: Gun of the Patriots has a script so flawed I could write an entire essay about it. Everything in act three sucks, act five is too short and none of the boss battles are fun at all. And finally similar to Sons of liberty if script is also excessively back-loaded and some of the characters become ridiculously melodramatic and depressed (and this is by metal gear standards).
Of course the things I like about each individual game but I've already written 435 words about it so I think I'll, I don't know, play metal gear solid or something.