I will try very hard to limit myself to the last 25 years, not the finest period for 'sportsmen' as I would define the species. However, the very lack of true 'sportsmen' in the last quarter decade should make only 5 or so really stand out.
1) Tiger Woods- I have never seem dominance such as Tiger's in my lifetime...maybe Richard Petty in the late sixties, but that's another story.
2) Michael Jordan- As fine a basketball player as ever strode the court.
3) Joe Montana- I know, I know, Dan Marino and others own the records, but I had to win one football game, Mr. Montana is the man to have in your huddle. I just realized ol' Joe barely gets in under the year limit! Dang, I'm getting old!
4) Michael Schumacher- Formula 1 racing gets the short shrift here in the US, but Schumacher in his Ferrari was SO completely dominant a couple of years ago, no-one could challenge him. Arguably, the finest driver of any kind of racing.
5) John Smoltz- A complete hometown choice...and I'll gladly take the arrows sure to come my way for this choice. Smoltz falls under the Montana principal: If I have one game my entire season is riding on, Smoltzie is getting the ball...the winningest postseason pitcher of his era. The most intense competitor ever to play for the Atlanta Braves.
Honorable Mentions: Roger Federer, Lance Armstrong, Alex Rodriguez, Roger Clemens
I should also mention that I do know there are great athletes in soccer (football) and various Olympic Sports, I cannot comment on their relative excellence because I don't know those sports very well. I'm hoping this thread will give us all the opportunity to learn about these deserving athletes.
If love is blind, how will it ever find a way?