I haven't been able to play Light Platinum, designwise, it gave to much too quickly and left me feeling daunted, because of the lack of simple linearity in the first half hour or so.
Flora Sky is pretty good, definitely well rounded. It had the opposite problem to Light Platinum in that there was very little variation in the way it played early and everything was explicitly told. That said it's the second best completed hack I've played.
Sienna was pretty decent of what I've played of it.
Fuligin could have very easily been my favorite hack ever, if the route design was better. I found that avoiding grass felt too easy and there no balance in level progression, kind of like trainer's pokemon were incredibly arbitrary in level and it didn't pace well. Those are minor details and the second problem goes in part to fix the first so I don't mind it too much.
Pokemon Brown is pretty epic, but as a mainstay (and the goto example for scholarly work on the rom hacking movement in academia) it should be very good.
My favorite completed hack is Snakewood. That said it incredibly arbitrary, yet, from a writers perspective it is incredibly well paced and made. There are very few loose ends which is a common trap in that type of game as it is explicit in what is required and what isn't. Anything that would be a problem adds to the charm of what is a quite snatch and grab hack. I find that I love it though.
However, and this is amazing considering it is only a single gym long, by far the best hack I have ever played is Pokemon Identity. And I am so sad that it will never be finished. This hack had me in the feels. This is the type of hack I'd love to be able to say I had the skill to make. And this is the type of experience I want to create in my games. It takes about two hours if you do everything you can in it, and about 40 minutes otherwise. But it is time very well spent.