Most people like both of them equally, such as myself and my friends.
Some people don't, either because they don't like gore (DooM), or they don't like Star Wars (Dark Forces) Some people like cutscenes, some don't. It depends what you like, I like both so I am a fan of Dark Forces and DooM. I'm sure many people will agree with me on that. I play both at different times during the year, month, week, or day.
I've changed the Dark Forces Info from last time because someone left a good statement in my guestbook. He said in hid message that he liked both DooM and Dark Forces. I couldn't agree with him more.