The newer Monte seats are definitely nice, as are the newer GTO seats that some people have swapped into G bodies. Some of the newer seats tend to be a bit bulkier though, and can be harder to fit into the amount of space in a G body. Most GM bucket seats (not all, but most) manufactured over the past 30 years or so have the same seat track bolt mounting pattern as the original G body bucket seats, and are therefore interchangeable, as long as you use the proper G body bucket seat tracks (power or manual).
This past winter, I installed a pair of bucket seats from a 1996-98 Grand Am GT in my '84 Monte SS, along with the rear seat that came out of a 1984 Buick GN that had the Lear Seigler seat option. The Grand Am seats have seat bottoms that are slightly longer, so they're more comfortable for people with longer legs. The driver's side seat has a manual lumbar adjustment, which makes it a bit more comfy too. The rear seat from the Buick is much more contoured than a stock G body rear seat, and looks WAYY better too. I had the seats re-upholstered to match the interior, and it turned out very well. Sorry, I'm not good at posting pics.
The pont that I'm trying to make is that you have a really wide variety to choose from, so try to look around before you make a decision. Try to take some measurements too, just to make sure that things will fit. Good luck.