That's true, the 1st game wasn't that much longer either. It would take about 1.2h to finish SF1 however SF2 can be completed in 44m and as ARandomGamer posted, SF2 was re-playable many times due to the different actions you may take. Plus in an era where Saves weren't standard, long games wouldn't be ideal to finish.
The music was also great, i don't think many games can top Star Fox 1 in the music department but Star Fox 2 did add more great themes to the series.
Menu themes, Eladard,Venom,Macbeth and Surprise Attack(Wolf's theme) were pretty amazing themes imo. It's a solid jam all around I'd say.
I also really dug Fortuna's theme, Flotilla Battle, Battleship, (inside and out) Battleship Victory, Mysterious Space Station, and the Credits Roll.
All in all, while I still think the original game has the best soundtrack in the series, Starfox 2 is also excellent in this regard.