(Note: Christian viewpoint. Can't speak for other religions).
I hate this argument. Here, I'll do it all in one post for you.
1. Yes
2. Yes
3. Yes
Now you're going to say:
"Well then how come, if God is perfect and not selfish, he demands us to worship him? Doesn't that seem selfish?"
Answer: No.
This is a common misconception, but God doesn't want us to worship him for himself, nor does he demand it. He asks it out of love for us.
Let's do this with a few stipulations.
1) Heaven is a perfect place. This is fairly well established; good luck arguing against that.
2) To get into heaven, you must be perfect. Again, hard to argue; heaven wouldn't be perfect if there were imperfect people.
3) Sin is an imperfection in God's eyes. Goes without saying.
4) So a person with sin cannot get into heaven. If sin causes us to be imperfect, someone with sin can never go to heaven because you aren't perfect.
5) EVERY person sins. Again, not arguable.
6) So without God's grace, it is impossible for a person to go to heaven. If 1-5 are true, this must be true as well.
7) God really wants to forgive us our sins (and has through Jesus Christ). Indeed.
8) But Jesus can't forgive us if we don't let him into our hearts. Basically, Jesus is right in front of you, with an outstretched hand containing the key to heaven. But if you don't believe Jesus is there, refuse to even see him, how are you going to take it?
9) So worshiping God and believing in Jesus Christ as our savior is the ONLY way to heaven. If 1-8 are true.
10) Therefore, it is not God "demanding" (in reality, asking) worship out of selflessness, but out of love as he wants to let us in heaven.
Yaaaaaaaay (by the way, this may have already been addressed; I haven't read the recent posts).