X-COM:EU is a lot of things. It's a fun tactical shooter. It's an atmospheric experience not knowing what's around the corner, but knowing that if something is, it won't have a hard time killing your guys. It is addictive enough to want to go on past the next encounter. But the most important thing that X-COM should be noted for is that it's a game about discovery. Every half hour or so you come up against a new enemy or threat, and as a result new things to research, and as a subsequent result, new weapons, armor and other means of taking the fight to the enemy. It's a game about progress.
While hardly as unforgiving as it's eldest sibling (although various tweaks in the second wave can bring it closer), the fact that losing your men and women as easily as you can means you're constantly cautious of the actions you take. In the process of the development of your soldiers, you become quite invested in their fate on the battlefield. By the end of the game, having a squad of titanically strong soldiers, knowing you've been with them from the start when they were rookies is a great feeling. In that respect, it truly is a game that gives out what you put in.
The controls have been streamlined (or simplified from another perspective) but the objectives and gameplay remain predominantly the same - turn based, probability of hitting based on distance, skill of shooter, etc.
Be forewarned, it's not perfect, nothing on the unreal engine ever is, and this game had a tendency to crash. That and the fact that you need a dlc to change armor color is a little cheeky, even if only a dollar or two. But when it works, it's a spectacular experience that you craft to your desire. I would definitely recommend X-COM.