I really hate that word, "Immersion", if we are to actually take it for what it really means, anyone who actually gets "Immersed" in game should probably be on medication and wear a helmet daily.
A better word would be Invested or Compelled. But I guess those are not "EPIC" enough to sell games.
It's also a bad word to apply to a game since it's a massively subjective property. One person can be "immersed/invested/compelled" in/by a game and another person might find that it's the most boring thing they've ever encountered and both people would be absolutely correct. It's not a property of games, it's a property of specific people's experiences with games. At this point you might as well just go with "fun" or "interesting." Even if the game does enrapture you for weeks at a time, there's a lot of different ways a game can do that; so talk about why it's compelling, not that it's compelling.
I'm not sure if anybody bases their purchasing decisions on promises of immersion, so it's of questionable value as a marketing buzzword as is.