Yes definitely. I love collecting the toys and merchandise, and looking at fan art. But I've only ever seen a few episodes of the show. My interest started when I was a lot younger - with the toys.
I don't think anyone has the right to say who is and who isn't a "proper fan." People can like My Little Pony in whatever capacity they like and they shouldn't be belittled for liking the merch/fan art etc more than the show.