I have
The Witcher.
I've not played it completely ... still playing - but it's awesome in one word.
Graphics is good. The locations are well-detailed. Gameplay is pure RPG and very immersive. If you love RPG genre - you'll enjoy the witcher a lot.
If possible get
The Witcher Enhanced Edition and you'll get two new adventures (though not very long) and almost all the glitches and problems of the original version has been corrected.
This is a must for RPG lovers.
RPG games are started with one character with some stats like, strength, dexterity etc. which has effects in characters play style. You'll given many quests which you've to finish before you continue to the next stage. This will also get you experiences.
Typically many optional sub-quests are to be found which you should complete to gain more experiences.
These experience points in turn will increase your stats so you become more powerful over the time.
RPG games are basically not played in FPS view. The Witcher has over the soldier view (like in gears of war) as well as isometric view (like in diablo II, neverwinter nights series etc.)
The witcher supports Mouse very well. keyboard will ease your gameplay complexity if used properly.
i hope this is enuf info for the time being. post if you have more questions.
resident evil is a different genre which may be answered by other members of this forum.
regards,