I can't really say anything about Papers please since I haven't gotten around trying it, while I've racked over 100 hours out of Xcom, so my opinion is understandably biased. I was one of the douches who ranted about the 2K Xcom remake, before it was retitled into "The Bureau", on the grounds that it didn't capture the feeling of the original game. When Firaxis were given the chance to churn out an alternative remake, I was intrigued enough to give it a chance and it didn't disappoint.
At first, I was very quick to find faults with the game, that I deemed lacking from the original title, like the limited squad size, restricted freedom to pick base location and omission of base defense. XCOM EU also has an odd early difficult spike but once you survive through the first 2-3 months of game time it becomes almost too easy, even at the higher difficulty levels. However, the game offered a more responsive gameplay and more excitement than the original title did and I can see how that can attract many people who'd normally not play through strategy titles.
The Enemy Within expansion was also a great addition that improved upon the gameplay, while introducing a base defense mission that I found sorely lacking.
In short, as a customer who's only played through one of the games in question, I consider myself very satisfied with it. Firaxis did a good job at taking a classic title and play the legendary dangerous line dance of creating a title that appealed to new audience without alienating the nostalgic fanbase. That alone is an achievement all by itself.
