I like large servers with lots of players, but some games don't allow many players. COD4 looks cool but has a max of 16. I like 60+. I presently own 2142, (haven't played in a while but IIRC the limit is high).
Any game within the last 3 years I will look at. Obviously if it's too old then there won't be many players left playing even if the limit is high.
Anything less than 32 does not interest me.