XCOM: Enemy Unknown, is a video game in name alone. It runs on a PC, has flashy visual effects, and was developed by Firaxis (famous for the Civilization series). However, this is more of a board game than Robo Rally (a great board game, worth looking up if the reader has never heard of it): you move pieces, roll dice, and swap turns back and forth. One could recreate the entire game with pencils, paper and a random number generator, but that's really not what makes it a board-based experience...
Card, board and video games are separated from each other by a few key mental concepts. Tying board and card games together are the transparency of their rules. When one plays Solitaire or Monopoly, one knows exactly how to play. It's implicit in the nature of card games: without knowing how the game works, one simply cannot participate in Go Fish or Crazy Eights. In board games the rules may be written on a card or in a manual and each player ends up learning the game. Card and board games also put all actuation in the hands of the players: the bank isn't going to reach out and take your money in Monopoly unless you put the little strips of paper into it. Video games draw a wall between players and rules by controlling these crucial steps of evaluation and manipulation, often by hiding the mechanics (do you actually know how the warthogs work in Halo?), and always by handling play progression (if you wanted to, could you stop Mario from descending?). In XCOM every facet of the game rules are on display: a plasma rifle deals exactly nine damage, with a 66% chance to hit (roll a 3 or better). By knowing precisely how each element fits together, players can immerse themselves in the simulation on the board as opposed to observe and modify an activity happening outside their reach, just as chess and solitaire players do.
A second divisor evident between these three types of gaming is time. Board games are almost exclusively turn-based or simultaneous: while a few involve a sand timer or a buzzer, time isn't going to proceed in analog. The shoe will never walk around the Monopoly board at the same time as the top hat by design, not merely by necessity. Card games hold a similar niche, but in space as well as time. No grid or board means no representation of distance, and only discrete markers matter as in the case of the decks and hands of Blackjack or Poker. Video games tend to balk both traditions: distance is crucial to any game with a world space, and a game world will proceed without the player if it has something to do. XCOM has a discrete board with squares, obstructions and player pieces, but takes turns between players, putting it firmly into the board game frame of mind. Therefore, I posit that despite its electronic trappings, XCOM is truly a modern board game.
A few elements in particular bring it to the board gaming audience, but the software keeps its computerized opportunities close at hand. The basics of cover and accuracy are solid and immediately understandable, and the game reaches to keep players informed (to the point of putting offense and defense breakdowns within easy reach). However, as Warhammer 40k fans know well, distance and line-of-sight calculations are a tedious affair to handle with pencil and paper. XCOM handles them with alacrity and aplomb, keeping the pathfinding and line of sight where all can see them while allowing the player to focus on higher-level decision making. Both sides follow the same rules, keeping the gameplay reliable while allowing asymmetrical strategy (the aliens certainly don't use pistols for long). By taking advantage of computing power the game can provide an opponent for single players, make simple operations quickly, and keep the dice and cards moving without interrupting the flow of play. Furthermore, it can keep track of player progress, saving and loading in the background so character sheets and spell ledgers don't need to come into the picture. Anyone forced into playing the banker or sliding the tiny pieces around a Risk board can appreciate the improvement. Finally, the virtual nature of the game lets developers and players alike tweak or expand the game: it's not quite as easy as house-ruling money from free parking, but it can also share much more advanced concepts and make bigger changes.
If you haven't heard of XCOM before, go check it out, though you should be aware that there was a similarly named and closely related game back in the 1990s (If you're so inclined, play that one too. It is much harsher and more confusing, but every bit as captivating). From an electronic or a cardboard point of view, this is truly a game worth playing.