For me it's incredibly simple, Elite was my first space sim. The 80's were a great time in game development, new genres were being invented almost every year, and being inovated, refined and improved on constantly (both technically due to vastly increasing processing / graphical power and gameplay wise). All the first's hold a special place in my heart, Wolfenstein 3d, Dune, Bard's Tale, Elite, King's Quest, Theme games, Railroad Tycoon, Civilisation, Microprose, Silent Hunter, Red Baron, etc.
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To expect the same when older, much more jaded and with a lot of other similar games to compare to would be delusional. Gaming has advanced considerably, Civ 4 is far superior to Civ 1, but doesn't hold the same magic.
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I could make a massive list of improvements, but that would be highly subjective. Some want ED to be a clone of Elite, some want a ED/Eve hybrid, some ED/Freelancer and others ED/X. Personally, I'm not bothered, but I do feel it certainly needs something extra. Something completely new would be ideal, but it's not the 80's anymore and a lot of things have been done before, so incorporating aspects from other space games, or even other genres seems a sensible approach.