i have never really been big into sports. In real life, that is. Sports games i tend to not enjoy in the long haul, but there are some serious exceptions to that:
on the NES, i LOVE Tecmo Super Bowl. whenever friends gather at my house, we're practically guaranteed to play some TSB. i prefer it to Tecmo Bowl, as all the teams are included, the number of potential plays has doubled, and it's just more balanced and fun overall.
Back in the day we played lots of Double Dribble and Blades of Steel, but i haven't tried them out in years. Mike Tyson's Punch-Out was already mentioned as being a great game, but it is also unmistakably a sports game, so that counts as wel.
sports games really got good by the time we made it to the N64. i prefer mine more arcadey, less realistic, so i've tended to focus that way. NFL Blitz is awesome. Wayne Gretzky's 3D Hockey (which later turned into the NHL Hitz series) is fun. NBA Hangtime (successor to NBA Jam) is amazing. i really liked All Star Baseball '99, but YMMV on that one.
Take it a step further and games like Tony Hawk's Pro Skater or 1080 Snowboarding were hugely popular and a lot of fun too.