Of course, what someone decides to do with their time is their own business, be it playing covers or writing originals. Both have their pros and cons which have been stated and will be restated over and over again. Still, it's hard for me to believe that people can sit there and say that one is objectively better than the other. Play whatever you like. For me, that means writing and playing originals.
I like playing originals because it gives me that creative outlet everyone likes to bring up. It's nice because appealing original music just kind of happens if I sit down with an instrument, which is probably one of the reasons I like originals, that is, because it comes naturally. I'm also a writer (of words, I mean) and I write a lot of poetry, so lyrics are never in short supply. Additionally, for me, there's no better feeling than standing on a stage and performing a song that you wrote for an audience of people that are just excited about hearing it, maybe even more than you are about playing it (this is ideal).
That being said, I have to give credit to people who perform covers as well. Although I've never performed with a cover band, it's not something I'm against, necessarily, it's just a matter of time constraints. Music isn't just about being a "creative outlet", certainly, it's also, and perhaps more importantly, about having fun! And covers are fun. You get to play songs with other musicians that people have been enjoying long before you came around and started rockin' them; these are songs that people are familiar with and already love, and they're going to be stoked to hear them performed live. And I could imagine it's pretty fun being a performer in a cover band as well. I mean, I play my favourite bassists' lines and such on my own time outside of my originals band, but cover musicians take this to the next level by finding other musicians who love the same music as they do and work together to recreate it live for the enjoyment of others; I can definitely see the appeal.
Essentially: I prefer originals but covers are nice too.