Personally the only way that you could possibly get away with kyle as ion would be to have a SANE hal working as the parallax. Ion would outclass parallax considering that parallax's origional power was mixed with oblivion to create Ion... Personally i think Judd Winnick's Kyle would win while Ron Marz's would fall flat on his face. otherwise give it to Hal.
It's not a fair fight. Kyle and alan has the raw power. Kyle has the imagination. John has the imagination and intelligence. (when john uses his ring to create an airplane you can actually see the working parts form first) . And hal has the will power. John has destroyed a planet. Kyle has held and exploding star. Well we all know what hal and alan have done. It would be a 4 way tie.
I can almost understand Kyle. because it was his "supposed destiny to be the greatest GL" And he has done some things like teleporting that I have only seen Alan do. But what is so great about Hal, give me some kind of evidence. I've seen John construct advance machinery using his ring and architectual abilility not to mention he served on the GL corp as well as the Darkstars and he has proven himself with every group including the JL. So we can all see where he has like a lot of experience. But hal, what did he do besides use his ring to form a giant fist and pummel people. Because he siphoned energy from his friends and fellow GL doesn't make him very strong. It just makes him devious. So I missed a few issues what is so great about Hal Jordan.
Hal has fought against much more powerful enemies than kyle. He is far more experienced. Before the glc was destroyed, the guardians acknowledged him as the greatest green lantern, possibly the greatest EVER. They have been around for bilions of years and even they admitted that theyt had not seen the like of hal jordan for a long time.
Alan has far more experience than either hal or kyle. Alan has totally internallised the power of the starheart. He isnt even human any more, he's made of pure energy, but only makes himself appear human throught force of willpower.
Kyle managed to be a great green lantern without the guidence of any other corps members and without the guidence of the guardians. He was all alone, and still managed to do well.
Mogo is a living planet, so could squash most of the other GL's.
Kilowog is back from the dead, and was one of the strongest, more veteran members of the old GLC. He was one of the 2 that trained hal Jordan (the other being sinestro).