Four, six or ten maps. Doesn't matter to me.
How large is one map/level, does it use repetitive objects, boring/ugly textures. How is the map setup, does it make sense?
It's quality before quantity for me? Rather enjoy 6 hours of solid and fine gameplay and entertainment, then 20 hours of boring shit.
Just look at FH2, hours of quality game play, because everything just fits perfectly together, not because they made 30 boring standard maps.