Could it be The Odyssey? The time period fits, and it features a boy in a coma who was transported to another world.
In the series pilot, 11-year-old Jay tries to join a tree-fort club, led by the tough Keith. As per the prearranged agreement, Jay has brought something of value to contribute to the club: a telescope that belonged to his father (who has been missing several years and is presumed dead). However, Keith double-crosses Jay and takes the telescope, denying him admission into the club. Jay tries to retrieve the telescope with the help of his physically disabled friend Donna, who uses a crutch and a leg brace in order to walk. Jay falls from the tree-fort, however, striking his head against a rock and lapsing into a coma.
In the coma, Jay finds himself in a fantasy world called Downworld where no one reaches the age of 16. Not having heard of adults, the children here have shaped society in their own ways, forming mostly tribal clans in the form of Clubs, such as the Pool Club and the Library Club. The biggest and most powerful Club, however, is the Tower, a brutal despotic police state run by the oldest kids, with Brad as the absolute ruler because he is 15, and "knows everything". Jay, not knowing how he has got here and aided by his friends Alpha and Flash (who are identical to Donna and Keith), embarks on a journey to return home — a place he can't remember. The journey becomes a quest to find his long-lost father, whose name happens to be Brad, who fell overboard from a small boat into a lake while they were on a fishing trip together and has not been seen since.