I used to play MMORPGs, back in the days. These weren't exactly "Massive" games though, as there wasn't more than two or three hundred players at once. My preference would probably go to MUDs, like
Achaea. MUDs are usually free to play (though some offer credits to have access to special advantages, and, above all, to support the game), but are based on text rather than on graphics.
Download limits make broadband virtually useless indeed (well, unless no ISP offers unlimited access at slower speeds). I believe the amount of downloading/upload done is very low, since even my modem at 33,6 kbauds had no trouble handling the games. Of course, spending a lot of time on such games would probably result in high downloading/uploading, so.