Omega Factor straight up reeks of a limited budget with it's enemy variety in stages and there's quite a few instances of slow down whenever there's too many enemies on the screen. Those problems fade away though when I'm playing it since there's so much love for Tezuka's work, that even with my limited exposure to his manga/anime, I can't help but feel it.
They had such an excellent idea tying the progression of Astro Boys powers to meeting and connecting with characters not only from Astro Boy but from various other of Tezuka's works. I never actually watched much Astro Boy but I was shocked when I saw Tima from a movie I'd seen a handful of times, Metropolis.
As for the gameplay, it's nothing that's going to blow you away but it's really fun, solid, and bite sized action. The stand out segments are the boss fights against other robots. I highly recommend it if you're into side scrollers.