Why you're debating of Hulk surviving into space, he needs to breath, of the GL don't throw him in the sun, he just put him a sector of the galaxy and Hulk couldn't avoid to breath for eternity, he would die.So he's defeated.Namor would be a match for Superman only if Superman is surrounded by Kryptonite chains and his in water.
Also would be fun to see how Hulk can hold is breath for days but he's too much far from the Earth to reach it before he die.A GL can also open portals, maybe Hal or Kyle just needs to teleport the forcefield cotaining Hulk on the moon of a planet in a far far space system, and Hulk will die.
It's easy to do it for a GL.
Now i'd like to read other fanboy ideas.Maybe Hulk saving himself pronuncing HULK SMASH and a Djinn would appear to save him.Lol