If what led to believe, http://www.escapistmagazine.com/forums/read/326.68619-Frontier-Elite-II-A-Retrospective-Review. And here the http://www.classicamiga.com/images/stories/jreviews/games/F/manuals/Frontier_Elite2%28map%29%28scan%29.jpg. There was also a bit of discussion about large ingame map in this old thread one can look at: http://www.gamesas.com/index.php?/topic/1091456-large-video-game-worlds/
That looks like a port of the original Elite game for the BBC Micro (that I still have). Apparently a scaled-down one, as the first version covered multiple galaxies with a Hyperspace jump between them. You had a number of maps like that, one for each Galaxy. That game was probably unique in using two different screen resolutions at the same time, one of which was monochrome, and the other color! I suppose you could consider them a single game, though, and include Freelancer as well (since it was based on it). So maybe Daggerfall is #2, but I'd expect there are a few more interplanetary games out there to push down the list.
However, in Elite etc. I don't think you ever land on a planet's surface, just visiting the orbiting stations, so you could argue they have no planetary area at all.