Well, here are a few complete ones I admire (I can comment only on performances, not labels and remasterings):
Dutchman: The 1955 Bayreuth with Kna, Uhde, Varnay, Windgassen and Weber. Uhde is becoming a fetish of mine. He's an amazing singer with a haunted quality in his voice perfect for Wagner's not-quite-normal characters

lol

, and has the rare ability to express extremes of drama without ever losing vocal focus. Hotter and London were other great Dutchmen on live recordings from that era, but I think this one is special.
Tannhauser: I have no recommendation.
Lohengrin: another strong performance from Bayreuth: 1953, Keilberth, with Windgassen, Steber, Varnay and Uhde. This was a great night for all concerned. Windgassen is not a real Lohengrin vocally, for my taste, but of course he's always an intelligent performer. The others are splendid, with Steber simply beautiful, Varnay wonderfully witchy and powerful, and Uhde the greatest of all Telramunds, as much victim as villain.
Tristan und Isolde: From Bayreuth: 1952, Karajan, with Modl, Vinay, Malaniuk, Hotter and Weber. Really intense and human, even for someone with an aversion to Martha Modl's voice

(she's a great artist, of course). From Munich: a live performance, 1950, under Kna, with Treptow, Braun, Klose, Schoeffler and Frantz. A very strong performance, with Treptow a surprisingly fine Tristan (I wasn't acquainted with his work) and a chance to hear Kna. Of course there's the '66 Bohm from Bayreuth, which everyone should have already.
Meistersinger: I haven't kept up with this opera on records. I've talked about the '56 Kempe and have been happy with it over the years.
Ring: The Krauss, Keilberth and Knappertsbusch '50s Bayreuth cycles all have their fans. There are many singers in common so perhaps it comes down to your taste in conductors. Then there are the live Furtwanglers from La Scala, and his RAI cycle. One must have some Furty, but casts of both are uneven. La Scala, 1950, has Flagstad. I don't care for the cast on Furty's 1954 studio Walkure (Modl, Rysanek, Suthaus, Frantz).
Parsifal: I've lost count of the number of Knas from Bayreuth. I'm not enough of a fanatic (believe it or not) to try to keep up, though it would be fascinating to trace the changes and continuities from 1951 to 1964. There's also a live Karajan Parsifal from Vienna which is highly regarded as a performance but apparently has rather poor sound. I've made some comments on your "2015 TC most recommended opera CD's and DVD thread":
http://www.talkclassical.com/36891-2015-tc-most-recommended-26.html?highlight=parsifal
There are many important historic recordings of excerpts made before it was practical to record the complete operas. Arguably the greatest examples of Wagner singing are to be found there. I'll do another post with some of those.