After making sure of getting the essentials & the cheaper and readily available options of with an abundance of minor & bigger hits, I went into the 12" arena.
One of the first things I came across was the 12" 80s series (https://www.discogs.com/label/352352-1280s). These proved to be a real jackpot and still stand as one of my favorites to this day. Luckily I was able to get most of them in decent (used) condition. On the other hand - unfortunately, looks like I was just about too late with one of the biggest / most soughed after series - the so80s by Blank & Jones. Of course, some of the volumes and still easy to find, especially the ones starting with volume 6 and beyond (except for no.

The other compilation series that remains very popular is Ben Liebrands Grand 12"s. This doesnt cover the 80s exclusively, as we all know, but as some others, it has its advantages & drawbacks. The sound quality - the work that has been put into getting the most out of these to sound as good as possible is well known and documented. The same goes for so80s series as well.
The Razormaid series in a category for itself and I cannot even hope that I would get my hands of a decent number of these volumes in a fair amount of time.
There are others - for example the quite popular budget compilations like Twelve Inch Eighties that have their share of the market.
Retro-Active - Rare & Remixes (7 volumes) is another very interesting series, but quite controversial apparently because of the sound quality of the recordings.
I have not been able to test it for myself thusfar.
Classic Alternatives looks appetizing as well but doesnt easily come by outside of Canada & The US.
Dance Classics - The Pop Edition comes to mind as well, but after browsing through its many volumes, sounds like a bit of a hit & miss type of thing. The art of making a good quality free flowing 12" compilation with no expandable mixes doesnt look to be as easy as it might look like at first.
The one that I have my eye of right now is Maxi-Pop (Contrasena Records) - a Spanish label with a great (different kind of) selection of tracks.
So, I would love to hear from other members here ..... what are your favorite 12" compilations (past & present) with regard to track selection & sound quality ? Which ones would you recommend going for ?