I had the pleasure of finally telling myself to watch the original series last year as some of my roommates are really big fans of the series. They insisted I would really enjoy it, and by the end, all I could really say was... yep. They were right.
Fast forward to present day- I still haven't seen the live-action movie adaptation (sounds crazy to say I want to watch something so widely hated, but the idea here is that I specifically want to see how badly they messed it up) and I also watched a bit of The Legend of Korra after I finished watching The Last Airbender. I had done a bit of extra research on the I.P. between my original viewing last year and when the new Netflix adaptation released, so while I still definitely wouldn't call myself an OG fan or anything, I felt pretty caught up by the time my roommates wanted to see how the Netflix adaptation turned out.
The general consensus seems to be that this new Netflix adaptation is better than the live-action movie but worse than the original series. How faithful a remake should be to its original version is a topic that's been very divisive in recent years, and this adaptation definitely goes the route of wanting to differentiate itself so far. We finished Season 1 a couple weeks ago, and while I definitely understand the gripes that longtime Avatar fans are going to have with this adaptation, I can't say it's a complete downgrade either. The issue here isn't that the adaptation is necessarily bad per sé, but rather the fact that the original Last Airbender series set the bar of quality and consistency so high that trying to match that, especially in live action, is either going to be extremely difficult or straight up impossible depending on who you ask.
The first two episodes of the Netflix adaptation were probably my favorite, but the direction the story takes starts to feel disconnected and dissatisfying from Episode 3 onward. Some research on Season 1's development can tell you why this is the case: during the early script writing process before the Netflix adaptation was even announced, the original series writers and the Netflix writing team had some... disagreements, to say the least, about what direction the series should be taken in. The original writers ended up leaving the project entirely, but it seems that their plans for at least the first two episodes still made it into the final release, as the disconnect between which episodes are being adapted into which episodes of the Netflix adaptation only starts in Episode 3 but continues like that for the rest of the first season.
As far as I'm aware of, the active development of a Season 2 of the hasn't started quite yet, but there are reportedly story plans in place for if and/or when a Season 2 is released. Whereas I would give the full original series a 9/10 (technically 27/30) rating across all three seasons and give the original Book One (Water) an 8.5/10 rating, I would probably give this first season of the live-action Netflix adaption a 6/10 overall, just enough to where I could still recommend it if you haven't seen the source material before but is still noticeably worse than said source material at the same time. My relative rankings for the whole franchise could still change if or when I decide to see the live-action movie, though.