Well, the cycle on the Nova forum isn't complete yet, is it? We have "What Override did better than Nova" and "What Nova did better than Override", but neither of them really hit the mark, do they?
The fact of the matter is, as I see it, that although Override as an 'improvement' on the original, and Nova is an 'improvement' on Override, they are all different in their own ways. EV had a very serious plot, which is beautiful in it's own simplicity, but as a friend of mine said, it's very lighthearted. EV:O, on the other hand, has much more basic humour in it (but less subtle humour), and it is, generally, larger. However, it forces you into making a choice of your government. For example, in EV, you're perfectly fine in a Kestrel. In EV:O, it's much more likely that you're going to end up in a government ship. Also, the EV:O ships were somewhat blockier and more colourful, which some people might dislike.
And now EV:N. The storyline is huge, detailed and realistic, you aren't thrown into piloting a government ship, since their are some very good civilian ships. But still, it's impossible not to avoid becoming part of a major government, and if you try not to, there's nothing to do in the game other than get blown up by Arachnids.
Looking on all three at once, I'd have to say that EV:N is definately the best of the three. Override is the most mysterious, and also allows for some very interesting arguments (whereas in EV, very few people prefer Confeds, and in Nova, there's no question that Polaris rule). But my favourite of all of them has to be the classic EV, where almost every ship is gorgeous, and every system seems special in it's own subtle way.
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-Lyat Esponer Corsair