Dark Forces - I've always wanted to play them, but they make me feel sick, so only really got into the series from JK2. But it'd be nice to have the entire series redone, DF + JK.
Sword of the Stars - yes there's a #2, and it's still fairly pretty IMO, but it's lacking and a bit meh. Which is a shame because I love the races, ships etc.
Tiberium Sun + RA2 - Still totally playable today, but them being a bit prettier would be nice.
KoTOR
Baldur's Gate 1 + 2- EE exists, but I'd like it redone on a newer engine, and not turn based like BG3 is. I prefer real time with pause.
Birth of the Federation and Bridge Commander
Those are what spring to mind, but I've probably missed a load. Black and White was mentioned and is a good shout since there aren't really any games similar to it (AFAIK).