Full disclosure: I'm a former member of HEAT, so I'm a self-identified fan with major entitlement issues
I can understand the annoyance of a Kyle Rayner fan feeling that Hal just stepped back in and tromped all over a character that had (eventually, tortuously) established himself as a pretty sweet character in the DCU.
But I think the additions of the Yellow Lanterns Corps and (to a lesser degree) the other Corps were darned brilliant expansions. And yes, they often didn't make a lick of sense (Emotions first started on Earth? Will is in emotion? Why is empathy so gol-durn weird? Why are there no males in the violet corps? etc.), but there was a whole lot of absolute comic book coolness for those first few years after GL: Rebirth.
I think the difference between GL: Rebirth and Flash: Rebirth is that the former felt like an inevitable make-good on a bad idea (Hal going nuts for no good reason and destroying the Corps), while the latter felt a lot like a present that no one asked for ("Barry's back? Um, gee, I guess that's okay. But he had a pretty good death, and his protege is doing a good job carrying on his name... what's that, you promise Wally won't get get shafted by this? Okay, based on how you've handled the GL franchise we're gonna trust you on this one, just please don't screw it up...")
In hindsight, it's hard not to argue that Kyle eventually got pushed into a ditch by the return of Hal (although I'd argue that Simon Baz and Jessica Cruz represented the final nails in his emerald coffin). But at least in the vastness of the GL mythology there's theoretically room for Kyle to shine.