The best of the ECM label

My favorites have been Gateway s/t and Gateway 2

ECM label had been for quite a lot. I like it and very often blindly pick up any record with ECM label on it and m'sure I'll simply enjoy that. It's a label that accommodates the best artists and known not only for extraordinary jazz, but neo-classical and neo-world music.
Pat Metheny, Miroslav Vitous, Terje Ripdal, Nana Vasconcielos, Meridith Monk, Chick Corea, Dave Holland, Charlie Haden and many more to list...

The best way to enter ECM's rather dense (but musically nutritious) catalog is to initially browse, discover an album or song of interest - then identify the musician(s) who seems to be most responsible for your enjoyment. At that point, use them as a guide to other releases in which they contribute or even lead. A music streaming service like MOG helps aid such sampling - then find it on CD or vinyl when you totally dig it. MOG has lots of ECM - whereas Spotify has none (perhaps some kind of Nordic/Teutonic rift?). Discogs.com and Allmusic guide catalog all players discographies across projects as well.

Being familiar with Nils P-M and his album Khmer - the next easy buy would be his album Ligotage (which was done the same year with very similar material). Before you leave him, check out his projects with Manu Katche as an off ramp to other artists (in particular Neighbourhood). That album is like a modern ECM family tree with lots of musical branches to climb up.

If you simply just dig the vibe of Khmer - then def try Arve Henriksen's album Cartography (in which Nils is present if not featured).

That should get you going.
Enjoy the climb.

My 2 cents...Check out Ralph Towner & Jan Garbarek on ECM - reasonably accessible. Playing off CTo007's suggestion, look at the other musicians they recorded with (e.g., Eberhard Weber) and try their stuff too. Usually, with ECM you get interesting, often beautiful and sometimes challenging music, not to mention great sonics. Would all labels were like ECM.

Anouar Brahem.