Well that's a matter of opinion I would have thought, a right I would like to think all of us are equally entitled to...
To place my comment into context it was made 7 years ago at which point I had just completed Book 9 Winter's Heart. My opinion of the series at that time was that it had suffered like a lot of EPIC series do. the infamous' mid stage sag'. What had started off as a really excellent series had begun to loose a degree of momentum for me by (as best as I can recall) Books 6 and 7. Things did begin to pick up a little after that but comparing it to GRRM's EPIC series (to that date) I felt that Martin's series was overall the better plotted and paced and contained the better overall prose.
Since then I have now completed the WOT and overall enjoyed it quite a lot with the final few books lifting the series to the level of the earlier books. I'm glad Brandon Sanderson was selected to complete the series as I think he did an excellent job guided as he was by Mr. Jordan's detailed notes.
Having said all of that I still like the ASOIAF series (to date) more than the completed WOT. Like yourself I am also something of a completist and have also read Jordan's original 'Conan Chronicles' (Conan The Invincible, Conan The Defender, Conan The Unconquered) which are amongst the best tribute works to Robert E. Howard I've come across. I can also recommend his story Cheyenne Raiders writing under yet another pen name of Jackson O'Reilly.
Above both Jordan and Martin however, I place Steven Erikson's EPIC 10 volume Malazan series. I don't know if you have tried this before but it is my favourite EPIC series of all time and comes highly recommended.
Cheers and welcome to the forum.