Preferably from somene who owns both or played both.

Can't get both

Believe me.Metal Gear solid 4.I have both.MGS4 is the best game on PS3 so far.Nothing is better.Online is way better than Fallout 3.The story mode is even longer. go to youtube and look at the gameplays for both games.

Definitely Metal Gear Solid 4. Did you check out the ratings on gamespot?
www.gamespot.com/ps3/adventure/metalgearsolid4/index.html

and Fallout 3:
http://www.gamespot.com/ps3/rpg/fallout3/index.html?tag=result;title;0

Metal gear solid got a 10 rating while fallout got 8.5. I own MGS4 and it's the best game I've ever played. Good luck whatever you choose!

I've played both and i enjoyed them both to a certain degree but they each have their own allure. if you want a more stealthy game go with metal gear. if you want anything else i would vote for fallout 3. they worked harder for fallout 3 than the makers of metal gear did for that game. this caused a very large payoff for the players of the fallout series... Fallout 3 has a story that works well with the previous games a while metal gear has been dragged on for too many games and should be left alone.

I've bought both, and returned Metal Gear after 1 playthrough (It's still a great game though, if you like Metal Gear series). Fallout 3 is amazing (Go figure, it's made by Bethesda!) due to it's graphics and do what you want style of gameplay. There's so many different endings, depening on what actions you took during the game. I loved how there wasn't a certain way you HAD to play it (If you run through the main storyline, it's about a 15+ hour game, if you do all the quests, it's 40+ hours, and there are SO many different ways to handle a situation). An example would be a side mission called Tenpenny Tower. This will contain spoilers, so read at your own risk.

Basically, a rich surviver still had a hotel of his intact, and was allowing other survivers to stay there, at a price. He allowed everyone to stay, except the ghouls (People who were mutated by the radiation, they were still human, but horribly disfigured). Tenpenny wants you to kill the ghouls, and the ghouls want to join the survivers. So....this leaves you with a few different options. You can help Tenpenny kill the ghouls (Which is what he wants), you can help the ghouls take over the tower (Which isn't what they want specifically, but it will work for them), you can try to make both sides get along, or hell...you can kill both sides! Pretty much every single mission (About.....30+ of them, they take about 45 minutes each) gives you the option to choose what you want to do...it's amazing!