This show definitely tops any sitcom I've ever seen, and maybe even any live action show. Each of the four characters has their own distinct personality. Both Will and Jack are gay but Jack seems more like an effeminate gay stereotype than Will does. Karen is so mean to be so nice, and Grace... well, the show's not called "Will & Grace" for nothing!
For six and a half years this was a barrel of laughs, but not only of laughs, of an everlasting bond between Will and Grace. Most people say Jack and Karen are the show, but there's a reason it's called Will & Grace. For example, imagine Rocky & Bullwinkle being about Boris and Natasha. Also, remember Joey. I don't really like how Will interferes in Grace's life all the time, but hey, it makes story.
Anyway, I highly recommend this sitcom, but be warned. In my opinion, after "Will & Grace & Vince & Nadine", the show just became not even close to what it used to be. The eighth season was just terrible IMO, and I didn't like the finale that much, but I guess it was a better finale than the season 6 or 7 finales would have been.