I haven't played EV or EVO in quite a while, and got pretty bored with EVN... kind of waiting for the ability to play the first to on Nova, but that could be a while, and otherwise I'll be playing them under emulation. I did think the other day that I need to start another game of EV classic; it has been quite a while. Personally I've had more fun in Override, and like those ship graphics best.. and know the mission strings far better :), but the simplicity and (I think) well done build up of Classic is what will bring one back to it.
After playing EVO and EVN a reasonable amount, I think that Classic has the happy medium between the two styles:
Nova has a 'you're only playing this to get the one string done' style, and it irks me terribly when someone says to keep a look out for more missions.. then it gets boring! I find there just isn't nearly as much fun to be had in the Nova galaxy - probably a combination of most of it being uninhabited and a lot of it having awful hyperspace design laden with dead ends, i.e. Fed / Auroran space - and the fact that you don't really bring about any changes in the galaxy (a la EVO) even though the missions tell you that you pretty much changed everything there ever was.. and they are always amazed by your combat skills even though (speaking for myself) half the time the enemy were all dead before you even got to them!
Override's style of having multiple strings available for the one pilot, and at least 3 quite distinct areas in the galaxy, is quite nice.. but it is also a bit harder to believe - especially the fact that the UE haven't explored much past their borders. Missions are fairly continuous and if there is a break in one, there is no shortage of others to do. The fact that big battles are restricted to outpost type systems - interrace borders - also declines from the fun to be had a bit.. too much effort into setting up 'real' cultures, i.e. this planet gives the UE hyperspace fuel.. this one gives the Zidagar aligned crystals, etc.
The style of Classic is very different from both of those. The story is very believable for a start, and the fact that you get to follow it through quite far is good. The ship range is modest compared to the other games, but there aren't any obvious omissions. Outfits, including secondaries, are simple to work out and use, compared to EVN where I've only tried to once, bewildered by the selection! Classic string missions have gaps in them - I think they worry more about combat / legal status than the other games - but there is plenty to do to fill in those gaps... the galaxy is well-designed, allowing for many places for fighting, while keeping hyperspace routes sensible - if you want to go somewhere, head in that general direction!
I could go on, but I'd say I've covered most of why I still would play EVC.. and probably will in the next few weeks :).