When evaluating power, current not projected, it's more about things like bat speed, strength, back spin, and distance than it is the actual number of home runs.
We see many HS players every year and especially last year, that have very good raw power. Kids that have the ability to easily hammer the ball out of Major League Stadiums. When I say many, it's still rare when taking all players into account. Kind of like kids that throw over 90 mph, there are a lot that can do it, but overall it's still rare.
So you have current raw power (ability to hit the ball a long ways) and current power (ability to hit the ball a long ways frequently). Then you have developing power or power projection (Often these are referred to as having gap power). Though it could be said that everyone has power potential, not that many ever develop it. So you end up with a big number that lack power.
None of the above, by itself, will guarantee or eliminate great success. Most every player, even those in the Big Leagues, lacks one or two tools. But power is heavily considered by most every evaluator. The home run helps win a lot of games.