For 2.0 they redid a lot or all the CGI with modern technology also various scenes were re-done if I recall but I haven't watched it in awhile. 25th Anniversary preserves and cleans up the original version.
If any of the older movies were produced on 35mm film they would look very nice especially if they have already cleaned up the film for a prior remaster, they might scale up to 6000p even. 16mm does max out around 1080p when converted though but they might have some techniques to get more out of...
If the Japanese releases came with English Subs I would seriously consider it for Macross and Macross: DYRL. I am really considering buying the Japanese release of Macross Plus though, but by accounts only the movie has subs while the OVA does not. Oddly the OVA does have the English dub though.
Seinfeld would probably require a process similar to what they are doing for Star Trek TNG. I could see them possibly releasing an upscale in the future but a complete series rebuild doesn't seem likely.
If that is really going to have the Japanese soundtrack with Subtitles I might pick it up. But doing some further reading, it's dub only despite what Amazon says, so screw that crap.
I'd buy Macross on blu-ray if it was ever made available here, I still refuse to pay the Japanese price. Freakin Harmony Gold just needs to die they are like a Macross patent troll.