I have been playing The Elder Scrolls: Legends (TESL) for quite some time now, and have just recently started over again in Faeria and Duelyst, and I think TESL is actually the most generous of the three. The difference is the ability to grind the AI for dust, er sparks...er Memoria, soul gems
You can get 300 gems per day, and with an aggressive deck those games are usually over by turn 5-7. I can usually grind out the 300 max in just over an hour, and its actually kind of fun, since the AI plays so quickly. So, if you're missing a legendary for your deck, you're guaranteed to be able to craft that in 4-5 hours of play over 4 days. It makes it seem as if no deck is really out of reach, and that keeps me coming back.
The gameplay is slightly more involved than Hearthstone, I definately enjoy it more than Hearthstone now, but thats mostly because of Hearthstone over-saturation in the last couple of years. I will play it alot when it finally comes to iphone. I have started Duelyst because I think that it will appear on iphone sooner, (they are in beta testing already). TESL will work on ipads that Faeria wont work on, as well. All three are great games, in my opinion, its just a matter of which ones I can get my friends to play first.