I remember the first game being pretty good overall but I never played the sequel.
Its got basically the same gameplay, just more levels and there's also a Megaman X-like element where you can find parts of his "Super Nerd" gear (that autistic getup he wears in the Super Mario Bros 3 review) and each part you find gives him a new ability...like loafers you find in the tutorial that literally let you cling to walls like in Megaman X.
Basically, the games feel to me like Megaman meets Celeste with a dash of Contra. I think I have an advantage in that I'm playing the Switch versions, which are a remaster and add in things like the normal difficulty giving you unlimited lives (hence the Celeste comparison). I've heard before this the game was really frustrating.. that original mode is now considered the "hard" mode.
That said, there are changes they made for this version (Which I know about because of videos) that I wish there was some way to revert. For understandible reasons, they had to remove cameos from other Youtubers... the biggest affect of this is that in the sequel, you originally got to fight the Nostalgia Critic at several points. But he's been replaced with Fred Fucks.
But Fred (who was always the boss of the first one) is the biggest thing I wish I could revert. The first game was made before the Life of Black Tiger review, where he was played by Gilbert Gottfried... and the remaster rewrites his dialogue (and changes his sprite) to make him match the Gilbert Gottfried interpretation.
Which honestly, I would prefer if they hadn't done that. I would just rather there be multiple Fred Fucks who all behave slightly differently but all claim to be the AVGN's enemy. Really tho I just think the version introduced in the Life of Black Tiger review is a one-note joke who quickly becomes tiring. He's fine for one review, but he did not need to come back.