Uhhh, if you want an example that fits inside the narrowest brackets you could possibly throw up then sure, I would go with anything in the Grand Theft Auto series since Vice City. Or saint's row, or far cry, or X3, or kerbal space program, or literally any other game that isn't a "traditional" MMO like ED is apparently trying to be now.
ED always felt like the space equivalent of GTA Online for me, a large sandbox you can flute around in for your own amusement or to co-operate/compete with other people having their own little mad adventures. It's been straying from that since launch for me and I no longer feel like I'm supporting the same game I was 6 months ago. New features (most notably powerplay) have only added to the grind and repetitiveness instead of replacing the grind with meaningful enjoyable interactions. I respect that you don't see it this way, but don't try to brush the problem under the rug just because you don't think it personally affects you.
I was of that mindset until it started affecting me. As soon as your personal goals in the game become anything that requires grinding just to achieve, support or maintain ("I want an anaconda!" "I want to do warzone PVP!" "I want to take up piracy!") the flaws in this game will slap you square in the face.
Quite a poor comparison, you chose games which on Steam have median play time of 15 to 17hrs, same as ED, and some of them have been out for years, with max playtime of about 80 (for discernible number of players). This applies to KSP, Far Cry, Saints Row games and even GTA series, except GTA V which has the median of 37 hrs, and up to 150 max . You can check it out on SteamGauge.
Guess what, even ED, which has been out for a couple of months, already has median of 17hrs, and max of over 150hrs, which excludes most of the players who started before March, so ED is doing at least as well or better then most of those games that you noted for "longevity".
Sum total, as on most forums - there is an issue of perception, players would want more than they got, and there will be an unhappy, but vocal segment of the community. So be it, but in principle, short of pure multiplayer games, there is nothing out there which offers the same longevity play-time wise, as ED.