Probably near the bottom of a top 20, if that.
Ginobili never had to carry a team like the rest of these guys (you could argue he never got that opportunity as well but

) and I can't imagine a Ginobili-centered team being any type of real threat in a playoff series.
You got, off the top of the head (no order)... Michael Jordan, Kobe Bryant, Allen Iverson, Dwyane Wade, Vince Carter, George Gervin, Jerry West, Reggie Miller, Ray Allen, Clyde Drexler, Earl Monroe, John Havlicek, Pete Maravich, Joe Dumars, Sidney Moncrief, Mitch Richmond, Sam Jones historically, David Thompson... not to mention guys who played some shooting guard earlier in their careers but ended up mostly small forwards (McGrady, Pierce, etc.) I'm not sure if put into the same team situations that Ginobili would have been considered any better than Michael Finley, Michael Redd, or Joe Johnson.