what do you think about "hybrid" game? the game im designing is an fps/rpg. the rpg elements come level building skills such as aim,speed,stamina,lockpicking etc.

Generally any genre can implement RPG elements and be all the better for doing so (probably because the RPG has no set requirements for view, control etc.).

As for the FPS/RPG, the game that springs to mind is Deus Ex, which had a few RPG elements. In such a system, the levels must be designed with extra care to ensure different characters can still compete - for instance if your character sucks at both hacking and lockpicking, can he still make it through the level? Deus Ex always gave the player several ways of tackling problems, including a brute force approach if all else failed.

Another good design, I feel, is the 2D platformer-rpg hybrid. The classic, of course, is Metroid and Super Metroid. Maple Story is pretty novel too, but the poorly-implemented hit detection turns me off of the game.

There's lots of good hybrids out there.

A lot of my favourite games are hybrids or fall within the cracks of the defined genre types. One of my favourites was Magic Carpet, which might be described as a sort of FPS/flight sim/strategy hybrid. Or Sacrifice, which was a third person action/tactical strategy sort of game.

The hybrid on itself isn't a bad thing, it's how you work it out. System Shock and Deus Ex, and to some extend Tron 2.0 all featured an RPG-like stats system, and No One Lives Forever 2 did as well.
Personally, I like such a system, as long as it isn't taken too far, e.g. too many stats to keep track of, neither do I like level-designs that assume a certain minimum stat value, like armor or jump height, in order for you to proceed - what if I didn't spend my points on that stat?

System Shock, as far as I played the demo, came off as too intimidating to me - a too complex statistics system, which for me slowed down the action to a cripple and detracted from the game. On the other hand, I liked Tron 2.0's system, which was gradually introduced and quite flexible to use.
In the end, it depends on what public you're aiming for. I would encourage you to keep it simple and effective, and gradually introducing the system to players.

the game im making will have combat like Half-Life and System-Shock 2

Hmm...combine the Legend of Zelda with Xevious and you get the old NES classic The Guardian Legend...Yeppers, hybrids can be GREAT! :D