I thought about it for a while and have compiled my pick of maps that I feel provided  great tactical layout, fun, and immersion.

#20: Metal Gear Online - Blood Bath
#19: Unreal Championship - Antalus
#18: Gears of War - Mansion
#17: Unreal Championship - Maul
#16: Halo 2 - Ascension
#15: Call of Duty 4 - Showdown
#14: 007: Goldeneye - Temple
#13: Gears of War - Fuel Depot
#12: Halo 2 - Beaver Creek
#11: Call of Duty 4 - Shipment
#10: SOCOM: Confrontation - Frostfire
#09: Halo 2 - Coagulation
#08: 007 Goldeneye - Library
#07: Uncharted 2 - Train Wreck
#06: Halo 2 - Lockout
#05: Uncharted 2 - The Fort
#04: Halo 2 - Ivory Tower

Of course Red Faction 1's version was better due to the better destruction (as seen below), the map was a blast to play on both games. It was simply two identical bases on each side with a small field in the middle.  Always great moments happened here.  Not to mention blowing away the other teams base was awesome.  Capture the flag was awesome here!

This map just felt great on all fronts.  Great sniper spots, great close quarter areas, secret passage ways, bushes to hide in.  Perfect size.  This map is intense and is always great fun.  This map is great whether it's day or night in the game.

Yep you probably already guessed it.  Facility is my favorite map of all time.  From the vents above the toilets, to the winding hallways, something about this map makes me want to visit in real life.  The opening and closing doors add a lot of tight situations.  Seeing each other through unbreakable glass, knowing where they are yet unable to shoot unless you go there is exciting.  Its a large enough map to not feel crowded, yet its not exactly open.  Its all close quarters and intense.