I can see why the Hyperdimension Neptunia delusion hit him in the right spots and at the right time (the financhu crisis and his depression over people blocking him on twitter) to do the most damage.
He already grew to despise the Christian god for failing to make all his wishes come true, and becoming himself a goddess is the ultimate power fantasy that "proves" to everyone else how he was, is and always will be in the right. The Idea Guys didn't tell him he was a goddess, they told him his Dreamcast was a portal to CWCville and then he got zapped by his old console when he left it on for 24 hours, believing on his own that was the spirit of the previous CPU goddess coming into his body and giving him her powers. In his mind it probably also explains his addiction to video games and why people are wrong to criticize him for it (even if it long predates the CPU nonsense)
The games itself, from what I saw in a single video, are very easy and you just have to mow down hordes of weak enemies over and over. The extreme repetitiveness probably appeals to him, along with the naughty female outfits, the flashy special attacts and the fact that they keep shitting out new games he can consooom. Things like Sailor Moon and Cardcaptor Sakura are not pop culture relevant at the moment and it's been a long time since they had video games (also with SM he probably has mixed feeling because of Megan)
I'm sure he chose the Commodore 64 over the Dreamcast or any other Sega console because it was made in 1982, his birth year. That said Chris does have a couple of ties to it, it was his first gaming console and Bob boasted to everyone willing to listen how young Chris learned to operate it before he could even talk, and how he would "master" any games he played in a few hours. Probably the only time Bob was proud of him.