This thread is going to heat up, though. Be warned.
There's a high probability but I choose to think it is possible to have a gentlemen's discussion about it
Here's my opinion, for what it is worth. I've been playing the X-Com/XCOM/X-COM/XCom series since 1997 and I didn't thought it possible for a remake to come out that was as nearly as good as the the original game. When I first heard of the remake I ignored it and kept my skepticism until I tried the demo of EU2012 then afterwards I decided to get the game.
Now, after two years of playing it, I consider it to be nearly as good as the original, but there are significant differences between both:
* Storywise, they are two different experiences. The 1994 version has the climax of the Cydonia assault, which is superior to the EU2012 Temple Ship. But the 2012 version's starting mission is much more darker and leaves the end open to the player's interpretation of what were really the aliens motives.
* On Geoscape, the 1994 version is better, with multiple bases and the air combat/dynamics. You need to find alien bases, you need to patrol for UFOs, to use the graphs for intelligence and to plan aerial fights. The 2012 version, on the other hand, has the panic system which makes things simpler but adds more pressure since it's easier to lose.
* On Battlescape, the 2012 version wins. The 1994 has random terrain, which to me isn't that big of a deal concerning map design and has the dreaded 'leaving the Skyranger without losing half your squad' moments. But the 2012 does one helluva job regarding attachment to your soldiers due to the class system and only bringing a max of 6 soldiers. I also prefer the 2 actions and the cover systems to the original, although the LOF mechanics are better on the 1994 version.
There's a ton of other differences, but I'll leave that for others to discuss.