UO was the best and probably still is my favorite cod, even though i haven't played it in years. Base Assault was one of the most fun gametypes I have ever played in any fps game. I can hardly remember any map names but I do recall Foy as it was one of my favorites.
The original Cod and UO were so great in that they were exclusively for pc. The pc community wanted huge maps with 30+ people in them and the developers delivered it. When cod2 came out as a multi-console game and Activision saw the sales of the console version in comparison to the pc version they quickly became more dedicated to the console version. The majority of console players wanted much smaller maps, due to the very small player limit created by the limited connection capabilities on the consoles. This is why there are no big maps anymore