I won't lie. I was initially attracted to Loki through the marvel movies. I can understand his (as in Marvel Loki) anger and angst (long story I won't get into). But, curiosity led me to go see how much he differed from Loki from mythology. The rest is history.
However, I think media is a great way for newbies to discover the stories and Gods ofteir ancestors. There are many fluffs and those only out for "rebellion" but there are a few who are true and stick around. I've met a few who initially started with Loki but ended up having relationships with other Gods. Loki is a good starting point for the newbies because right now, he is the most familiar and has the rebellion factor that draws teens like flies to honey!
Loki is the foremost deity I work with, so I know what he is like. Fenrir is not the same as Loki, he is not inherently "bad" and his mannerisms have nothing to do from the fact that he's Loki's son. I would say his behavior and negative connotation comes from the drama surrounding Tyr's betrayal and the Aesir locking him away. Loki is not inherently bad either, and can be a very positive helpful deity.
Having said that, I acknowledge that neither Loki nor Fenrir are deities of "love and light". Both of them have a very dark side to them. Fenrir, especially, is not a deity people can easily connect to and work with. But they're not all bad. It's not a black and white picture. Same with the Jotunfolk.