I played the first 2 and they were... fine, I guess. Kinda boring, which is surprising, given that parasites/worms is one of the more "out there" fetishes. Like, how do you make something so strange so... un-fun.
Maybe that's a little harsh. It's not like the first 2 were BAD games. I got a bit of enjoyment out of them. Maybe I'm just spoiled by how good some eroge has gotten in recent years. I still remember the days of *shudders* Meet 'n Fuck games. Those were dark times.
Anyway, wasn't aware that there was 3 and 4. I'll try this one and see if it makes an impression.