so your saying to buy metal gear solid?
No. It's the worst Metal gear game in the series (it's only a must own for fans of the series). If you haven't played the other games you'll be confused as fuck and in all honesty its not an action packed game like gears of war, halo, ect... It's more slow passed and it's more so a stealth game first than an action game. You usually don't go very far running and gunning in metal gear. It's all about hiding, planning, and blending in. So it's not everyone's cup of tea. I personally love the series I own every one, however 4 is most definitely the weakest one in the series.
I could only recommend this game as a rental it really was lacking to me (not in the graphics department or game play)...it's story was just weak. Considering this game is 80% cut screens and 20% game play story goes a long way. Seriously cut screens are anywhere from 10 mins to 40 mins long. So basically you play for a little and watch a lot (that I don't mind as I love me some metal gear), however when the story sucks you just can't get all into it.
Personally I'd recommend resistance 2 if you like FPS games and Dead space if you like survival horror. Dead space is just fucking nuts.