Fallout 3 On X-Box 360

I've enjoyed it but feel some warnings should be made as no game is to everybody's taste

This is VERY different to the Far Cry games (I have not played Zombie Island so cannot compare).
The Far Cry series is basically a first-person shooter with minimal "rpg elements" tagged on
Fallout 3 is an RPG developed to look like a first-person shooter. So it's more Oblivion with guns
..or (in someways) a first person Alpha Protocol or Mass Effect 1
The key difference is that RPGs are traditionally designed based on the principal that success or failure depends on the character's skills, etc rather than the players ability to operate the control making them a strategy game rather than an action game.
So if you do get it increase your gun skills to kill your enemies.

related to this in RPGs you tend to start out weak and become more powerful as you improve your skills and equipment.
Consequently, the moment you step out of the vault, you are weak and need to learn when to fight, when to run, when to swim through a radioactive lake to escape pursuers, etc.
When I played I headed in the wrong direction and was repeatedly killed by a band of raiders.  
As I progressed I became tough enough to take on a single supermutant but still had to flee their hunting parties
and I progressed even further and became supertough  ...

note - Save often ... because dying is easy

The original edition had a rather forced ending - it's better to get the game-of-the-year edition with the expansion packs, one of which allows you to continue after the end

Also note the game's setting -Washington D.C. devastated by nuclear war - it's a very bleak and atmospheric with devastated buildings and burnt skeletons-  I like it, some others don't