I can relate in regards to Mattingly. I grew up here and was an Astros fan, but the only individual player I cared about was Mattingly. Once he was gone I no longer cared about the Yankees, but I still get a lot of flak when I tell people who my favorite player was or that his autograph on my baseball is my favorite. That includes the ones I got when I met Stan Musial, Harmon Killebrew, and Rod Carew. I know, I'm crazy that way.
See, for me I was a big Clemens fan! So I followed the Red Sox and Wade Boggs/Mike Greenwell. I still follow them to this day, and I was so happy for them when they got their ring. Curse of the Bambino lifted! lol
In basketball, and I'll probably get negative rep for this LOL, but I loved Larry Legend. Dude could flat out ball, and while I am a HUGE Rockets fan, first time I saw Larry play was in the 1986 Finals against the Rockets.
In Football, my favorite player was Bo Jackson as a kid. I had the poster with the shoulder pads/bat. Almost all of his cards. I thought the dude was great. Read his book, "Bo Knows", which I remember being a good book, though I don't know if it was the fan in me or not....
As far as Houston sports goes: Dream, Biggio and AJ, all day. I loved the Oilers and I guess Campbell was my favorite, but I was young when I saw him play, other than that, I loved Chris Dishman and Ray Childress, dude was a hitter, well so was Moon, but that's a different story.
Sorry about that, I took a trip down memory lane on a completely irrelevant thread! haha