How many man hours does it take to make a game?

well the number of games needed to sell really depends on the budget and production costs.
and as for man hours well, that really depends on the game.
a friend who works for a game developer can be working on a game for around 8 months +

I've heard that Doom III alone took close to $20 million to make. Huge amounts are spent by developers in licensing fees (music rights, physics engines, video/animation systems, etc) alone. That's in addition to the company's own programmers, artist, directors, managers, etc.

Today's development team sizes and budgets are approaching Hollywood's major motion picture sizes. The days of one guy making a successful game on nights and weekends are long gone.

With MMORPGs, such as The Sims, WoW, etc., the hardware costs for their game servers must be staggering.

Yeah good games usually takes long time to create and millions of dollars in expense.