Sylvester Stallone scored a knockout with his Rocky musical by winning over critics on opening night with a big budget Broadway boxing bout.

The Hollywood action man spent nearly 15 years working on transferring his beloved boxing movie to the stage, and his hard work paid off as the the show opened at the Winter Garden Theatre in New York City on Thursday night (13Mar14).

Critics were full of praise for the show's star, Andy Karl, who takes on Stallone's iconic role, with The Huffington Post's Rex Reed, describing the actor as "the biggest thing since Hugh Jackman" adding, "He looks like a movie star... He is merely sensational."

However, it was show's big finale fight, which places the audience ringside for a boxing bout, which captured the best reviews, with Linda Winer of Newsday hailing the scene as "the most impressive 20-minute boxing match ever seen in a Broadway musical" while Mark Kennedy of Associated Press adds, "The final fight - a spectacular piece of theatre, to be sure - is so lifelike that it becomes surreal. We're watching a simulated fight lifted from a fictional movie but played inside an ornate Broadway theatre."

The Hollywood Reporter's David Rooney concludes, "The finale fight is so visceral and exhilarating that it sends the audience out on a high" and Terry Teachout of Wall Street Journal predicts the show will be a big hit, adding, "Rocky is a straight-down-the-centre commodity musical - but a damned fine one, maybe the best I've ever seen. A knockdown hit, in fact."

Stallone attended opening night with his family and a number of his Hollywood pals, including his Demolition Man co-star Wesley Snipes, Burt Young, who played Rocky's brother-in-law Paulie in the boxing film franchise, Whoopi Goldberg, and director James Cameron.