I guess it is Thief: The Dark Project
CORRECT! (insert funny winner pic here)
here is some info
1. was the game released after 2005? - NO 1998
2. Is it played from a 3rd person perspective? - NO its first person perspective
3. Is it an FPS - YES - labelled a first person Stealther by developers, also you shoot arrows (cant have said no as it is first person)
4. Are you fighting against aliens? - NO (garrett encounters humans, ghouls and animals, even weird wisp things, but no aliens)
5. Is it a console exclusive? - NO (it was not on console)
6. Is it a AAA? - YES ...? (it was very positively received - lowest score is IGN with 89,budget and marketing unsure)
7. is there more than 1 game in the series? - YES (thief 2: metal age, thief: dark shadows and the 2014 reboot)
8. Was it released before the year 2000 - YES 1998
9. Are there Nazis in the game?/ Do you fight Nazis? - NO see question 4
10. Do you play as a silent protagonist? - NO - garret speaks during cutscenes and during
11. do you fight non-humans? - YES - you encounter burricks
12. Does it have online multiplayer? - NO - thief was SP only
13. do you use magic in the game? - NO - however you can argue that the trickster uses magic, the question asked if YOU use magic - no)
14. is it a science fiction setting? - NO - its swords and bows
15. Do you face off against SHODAN in this game? - No, thats system shock
16. Are you a thief in this game? - YES you are Garrett, master thief
17. Is stealth a big aspect in the game? - YES it is regarded as THE stealth game

18. is it Baldurs Gate? - TROLL
Also, while searching for thief and AAA and what it is, i ran across this. And Its really interesting!