Earlier quoted context omitted.
Only the web version is ad-free. The iOS version has ads. Its longevity I believe will be greater compared to the Threes game. What makes you think otherwise - that Threes will stay on the top for longer than 2048?
2048 is Solitaire. It's exactly the same kind of game - the algorithm to beating it is dead simple and you win or lose by the whim of the RNG. As per the words of a person who plays Solitaire every day: "I don't play it because it's challenging, I play it because I need to play with something that requires no thinking for a while". Also, I don't have an iDevice or a desire to pay for a simple puzzle game, so I have n…
You're probably thinking of Klondike or Freecell. Neither of those require much thought and both (Klondike more than Freecell) are quite at the whim of the RNG.
But there are many Solitaires that are almost always winnable and require thinking and not rote algorithms. Try Spider Solitaire [1]. It's almost always winnable, but it will take you 20 to 30 minutes if you're good, and 40 minutes if you are not. I also quite like Sea Haven Towers [2]—it's like freecell, but the rules make it a little tougher. It requires some nice lateral thinking at times.
In those games the RNG only decides the difficulty of the game, not whether or not it's beatable (obviously occasionally it isn't, but it's very rare for both of those games).