After playing through Mass Effect 1 and 2 with a renegade male and then with a paragon female I began to get interested in role playing games a bit and bought Fallout 3 (also for Xbox 360). Before I start my first playthrough I'm interested in outlook customization like clothes and guns with different colors, so are there any shops or people for that or is Fallout different regarding what you can customize?

Fallout 3 (and Fallout NV) offer a higher level of freedom for character customisation than any game I've played. You have stats like strength and charisma, but also about 20 different skills as well as "perks" which help you in other ways. Also, the inventory is much more dynamic than mass effect. There are LOADS of weapons, clothes and other items to find, trade, or buy (I don't think you can choose the colors though). Also, unlike Mass Effect, there is much more of a sense of interacting with the enviroment. You can fall off buildings and hurt yourself. You can shoot your companions in the back of the head, by accident or design. It is great!!

I am a big fan of mass effect, and it is difficult to compare the 2 because they are a quite different experience. But if you liked one you should definately try the other.

Yes very different types of games. Both are great but in their own way.

I've only played Mass Effect 2. Excellent story and characters. However, although you get some flexibility with the recruitment, loyalty and misc missions, it is extremely linear. In some ways that's good because the developers can anticipate paths and form alternate dialogs and reactions.

Fallout 3 (like Elder Scrolls) is different. It sets up a huge world that you basically explore and interact with in whatever way you chose. The Main Questline is kind of secondary or lower, at least it is to me. Whereas in Mass Effect 2 the main quest line is pretty much all there is.

To the specific question of armor and weapon customization, you can't really do that the way you can with Mass Effect 2. But there are a variety of weapons, armor, and other articles you can use.

Fallout 3 has around 200 different places to explore. and another 100 places to explore that are un-marked on your map.

A lot of cool easter eggs, a lot of weapons, a lot of clothes (armor), a lot of customizations, a lot of NPCs, a lot of enemies. There are around 50-60 side-quests to do and there are about 10 many story-line quests. It's really fun, and make sure to buy all the downloadable expansions for it.

mass effect games are literally linear, fo3 is a wide range of exploration in the capital wasteland, i wont blame the comparison though, it is because mass effect is a sci fi, so mapping linearity is already expected, the thing that mass effect impressed me is the combat and the game play. Sure its not like fo3, but in its own sci fi scenario its one of the best 3rd person shooter there is. If you already played mass effect you already have an idea of the rpg platform so the adjustment when you play fo3 is minimal.