That's cause it IS the best. Old movies were fun when you're a kid... but at their core they're nothing but single fights dragged out to ~20-30 minutes with varying levels of expository rambling and bad/corny jokes, the only exceptions being Bardock and History of Trunks (which are not coincidentally the only 'canon' ones of the bunch with actual mainline narrative implications). Super Broly's animation was godlike... but besides giving Broly a bit of an actual personality and a green alien girlfriend it's just another 45 minute (VERY well animated) slugfest with Dragon ball Minus's retconning of Goku into anime Kal-El shoehorned into the beginning.
Super Hero on the other hand is the first real FILM the franchise has ever been blessed with. An actual narrative that isn't just "Goku and the Z-fighters fight an alien monster/roided up saiyan", characters with fleshed out human personalities that aren't just "I wAnT tO bE tHe StRoNgEsT", humor based around those personalities that isn't just Roshi being a perverted incel like in the old Z films, great animation (even if it looks a bit stilted when the characters are stationary) and fight choreography, real personal stakes behind that action that isn't some powercrept cosmic nonsense that isn't relatable or interesting... shyt's an actual fun, well-written movie. In a franchise who's theatrical releases have historically been nothing but glorified toy/TCG/video game advertisements and tie-in promotions.