I played The Quest for El Dorado (by Reiner Knizia) a few times after it came out last year, and while no other deckbuilder holds a candle to Dominion, I have to say El Dorado is the "Dominion clone" I've enjoyed the most (I've also played Clank, Ascension, and Star Realms).
It takes a lot of the typical deckbuilder mechanics described in many of these clones: play actions, play resources, buy cards which go in your discard, draw a new hand, shuffle when needed, etc. Instead of buying victory cards or earning points, players "race" across a variable hexagonal game board (which is randomized each game), passing obstacles and different types of terrain to be the first to reach "El Dorado." There's a nearly infinite number of different routes to victory, so every player will likely take different routes depending on how they build their deck. Taking the resource generation of a deckbuilder and applying it to the movement of your piece across a physical board is reminiscent of Clank, though different terrains use different card resources, and the randomization adds to replayability, unlike Clank's few set gameboards.
There are a total of 18 piles of purchasable different cards besides your starting cards with only 3 copies each. The market starts with just six of these piles which are the only ones you can buy from until a pile is depleted, and then the next player can buy any card, and thus choose which of the other piles gets added to the market, which adds some tactics of when to empty a pile. Unlike Ascension and Clank's rotating supply, this mechanic is pretty neat and seems unique among the deckbuilders I've played. With only 18 cards, it sounds like it might get boring quickly, but the limited numbers of each card and restricted purchase times, means every deck you build will be different and involves some healthy player interaction of when to empty a pile and when not to.
A few other differences, you only draw 4 cards per hand instead of five. Another neat thing, you can use excess cards in your hand to help buy cards (each 2 cards=one coin). Finally, at the end of your turn, you are allowed to put any excess cards onto your deck instead of discarding them, which is poses interesting choices for setting up your next turn (e.g. a have an oar I cant use this turn but next turn I'm probably going over water, so I'll save it). It's a neat puzzle to try and figure out the best route to the end, which cards to purchase, and how to set up your next hand. If you haven't played El Dorado, it's definitely worth a try.
What I really love about Dominion are the equal starting positions and that all cards are (usually) available to all players--rotating supplies add a bit too much randomness to me, and I never like seeing certain options suddenly closed off from other players just because it wasn't their turn when a specific card became available. I've yet to play another deck-builder that emulates these principles of always available cards, yet also infinite replayability, as simply and as elegantly as Dominion.