The Rocky 5 ending is a street fight between Rocky and Tommy Gunn, which Rocky wins with his family and the neighborhood behind him, and Rocky lives. In my opinion, the choice of a street brawl over a ring bout is the most interesting thing the film does. Tommy holds the title but not the respect, so the only fight that settles anything is the one with no belt, no promoter and no referee.
Compare how the saga closed its earlier chapters. In Rocky (1976) the climax is a title fight in a ring in Philadelphia, and in Rocky IV it is a bout in Moscow in front of a hostile crowd. Rocky V takes the stakes away from a ring altogether, and Terry Funk, a pro wrestler, choreographed the brawl, which is why it reads as a scrap rather than a boxing match. That makes Tommy the first opponent in the saga who is Rocky's own student, and the fight is as much about a trainer and his fighter as about two boxers.
It could be argued that the ending is also the film's biggest what if. Stallone's original script had Rocky die after the fight. Director John G. Avildsen told CBS Philadelphia in 2014 that the studio head said Rocky would not die, and that the studio changed the ending about two weeks into filming. Avildsen added that he felt the change hurt the film. A death would have made the street fight a final statement about pride, while the survival ending leaves Rocky standing in the same place he began.
The saga answered the question later. Stallone has described Rocky Balboa (2006) as a chance to give the character a better send off, which suggests that the Rocky V ending left the story unfinished in his eyes. In that later film Adrian is already gone and Rocky Jr. is played by a new actor, and Rocky V is the final series appearance for Talia Shire and Burgess Meredith. Perhaps the fair reading is that Rocky V is a bridge film: it strips Rocky of his money, his gym and his title standing, and Rocky Balboa builds the closing chapter on that.