Well the idea of Power Rangers being on Nickelodeon just drives the idea into my head of, "What if Spongebob loves Tokusatsu?" Looking at his overly cheery personality and being scared so easily, I guess he might actually like modern Tokusatsu over older Tokusatsu. Maybe he might not like Power Rangers because Super Sentai humor is crackier, but he might get a culture shock of older Tokusatsu. Now for his possible reactions to what Tokusatsu he may have wanted to check out...
Spongebob is most likely to like Kamen Riders post Ryuki because I don't think he likes nightmare fuel. He's too scared of it. For my thoughts, maybe he would like most of the sillier Kamen Rider seasons like OOO, Fourze, Wizard and Kiva. Maybe he'll like OOO the most because of Kougami who may resemble Mr. Haim Saban.
Probably due to Power Rangers Samurai lacking some real crack, he would probably go for Samurai Sentai Shinkenger because of the better humor. He might start off with Shinkenger as his first Super Sentai. However his favorite Super Sentai if he goes anything before Shinkenger would be Go-onger and Carranger. Most likely he will like Go-onger the best because that season was really stupid though I don't hate it, but I don't love it.
Well it didn't help though that Patrick Star likes Tokusatsu too and ended up writing the worst movie ever called Super Hero Taisen.