What does every action movie need?
A nasty villian that the audience can hate, and a good, tough hero that the audience can love. If these character premises are established and the plot flows, the final confrontation between these two arch-enemies should be breath-taking and keep the audience guessing.
Gladiator does this perfectly. The boxing scenes are gripping, intense and pull the audience out of their seats to cheer for the films two heroes... Tommy Riley and Cuba. The movie has a great soundtrack and a noticeable visual style that stays constant throughout the film.
Horn (the bad guy) played by Brian Dennehy and his sidekick Pappy Jack played by Robert Loggia are a great combination of nastiness. Horn is brutally evil and rules his underground boxing contingent with an iron fist, while Pappy Jack is a sleezy, humorous villian that compliments Horn's seriousness beautifully.
The characters have some depth, but not much. Who needs depth in an action movie anyway? Tommy Riley, Cuba, and Romano's stations in life and their particular choices are explained adequately enough for the audience to sympathize with their situations and want them to kick some serious ass.
Bottomline:
A kick-ass action movie. You will find yourself cheering loudly and rewinding parts because of their sheer intensity and visual, ass-kicking style.