For me, '2000s' means 2000-2009, so since that's the case, here's my Top 15...
1. The Descent
2. The Mist
3. Dawn of the Dead
4. Trick ‘r Treat
5. Slither
6. Saw
7. 28 Days Later
8. Shaun of the Dead
9. Ginger Snaps
10. REC/Quarantine (REC is better, but I loved Jennifer Carpenter’s performance in the American remake)
11. Final Destination
12. Bubba Ho-Tep
13. Rogue
14. Zombieland
15. 30 Days of Night