Not bad. The audio definitely needs attention, but you acknowledge that. I guess, you could try the text reviews, if you're still experimenting. But that would probably push it over a minute (or even 2).
I would leave out the category ratings. One overall rating is enough to me (especially for a GB game). You can mention graphics/sound/etc. if it warrants a shout out. Most people probably know what to expect out of a Game Boy game in that respect.
I can't believe you didn't mention/show the shooting sequences/levels of SML though. That was one of the best parts for me back in the day.
Don't take my critiques the wrong way, however. I like game reviews of all flavors. Just throwing my reactions your way in hopes of more and better

...just another lost soul...