Is it the only SM opening sang by a male singer?
For trivia's sake, there is a reason behind him singing the openings.
Back in the early 90s, there was a children's variety show in France called "Club Dorothee". Bernard Minet was a part of the cast. Saint Seiya, Sailor Moon, "Nicky Larson" (City Hunters), Ranma and several other anime were part of this variety block. (complete listing is here http://fr.wikipedia.org/wiki/Club_Doroth%C3%A9e
The themes were made to be simple but catchy, with corny lyrics to appeal to kids
Saint Seiya's is roughly:
The guardians of the universe, go to defeat evil!
Without a doubt, they will fight for an ideal world!