I find this a good post, so I respond to it.
First there are all kinds of solitary games and yes there are dozens of solitary games you can play at 4-5 hours a day. I'll give a few very specific ones: Ambush and its many expansions (board wargame), LoTR Living Card game, any serious wargame simulation without hidden movement. I played War in the East back in 1979 at 5 hours a day for 3 months long (yep I was a student back then and I always passed my studies in the first exams per year... So I had 3 months vacation
Of course then there are the games - casual or not - that you can play forever with a very HIGH degree of fun: Poker is but one.
But Hearthstone doesn't fall in that category. Not at all. It is NOT casual enough to replace Crazy Birds (stupid game too) and it is PvP based with a very (boring) hardcore surrounding these days.
Nope, not a lot of women will be attracted to it. And nope apart from the usual "gamers" crowd it won't enter general public acceptance either.
Part of that is due to the PvP kind of seeding, part of it is that HS is the wrong kind of game to be played for months long.
Will it penetrate the giant smartphone market? Nope. Can it be a hit on tablets? Let's hope for Blizzard, but frankly I think the "vogue" will be very limited, because most people will get owned by the hardcore crowd.
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TLDR So HS falls between two different markets: due to its PvP nature it falls out of the casual market and due to its boring "we play the same cards" and copying EVERYTHING from the internet in deck compositions, it will have limited interest in the long run.
I was one of the guys who thought it would conquer the world. Sadly it will not.
It lacks depth, it lacks casual, it lacks GOOD and LONG TERM interest.
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I am sad about it because I think the WOW franchise deserves better, but after the rape on Diablo, I am no longer surprised either.
Blizzard simply launched too many mediocre games: SC2 (far too PvP niche for a Blizzard game) - D3 and now HS.
And this is MORE than a personal opinion, as both SC2 and D3 hardly got ANY prices in the gaming community.
I am afraid Heroes of the Storm will go the exact same way: too hardcore for the casuals and too limited to play it for 10 years.
As it turns out in these last years, WOW was a very a-typical game even for Blizzard standards.
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Perhaps the Legacy of WOW is already too hard on Blizzard, but that's the way it is: I don't accept mediocre games from a company that gave the world the biggest MMORPG world to date.