I think the thing a lot of people over look when choosing a deck building game is who makes the game. This will basically tell you what kind of game you are looking for.
DC, Ascension, LOtR, Street Fighter, are all made by Cryptozoic. They are pretty much know for tacking themes on to pretty good mechanics. These deck builders are very fun mechanically and the fact that there are Superheroes or fantasy characters or what have you is very secondary to mechanical interaction. These games are typically not cooperative. The exception is LOtR which can be so when you are playing impossible mode.
Legendary is made by Upper Deck. Not to sure exactly what other (if any) deckbuilders they have published but I have heard here they tend to try to mix mechanical interaction with theme. I don’t own nor have I played it but I have little to no interest in it as well because of the semi co-op nature of the game and the opinions I have heard from others.
Rio Grand Games does Arctic Scavengers and Dominion. The former is an amazing deck builder hybrid where the theme feels amazing and the choices actually matter. The former I have not played but it have heard the theme still feels slightly tacked on, it is one of the deck builder games where you can get steamroller if you choose the wrong stragedy and turns can take forever (I. E. card combos feel infinite). They both include a different style of buying when compared to other games mentioned so far. On top of having some semi random cards you can obtain, you buy from set piles. This kind of buying doesn’t sit well with some people since it can make each game feel too similar.
When you start to get into the smaller publishers like Alaric Entertainment (Thunderstone), Game Night Productions (ShadowRift), 3Some Games Inc (Heroes of Metro City), Stronghold Games(Core Worlds), and White Wizard Games (Star Realms). You can typically find them building on other successful deckbuilders. For example, Thunderstone and ShadowRift are Dominion style deck builder with a twist that you are a also trying to defeat monster to gather a powerful artifact or defend a town, respectively. Heroes of Metro City is most similar to Legendary in terms of a team trying to defeat a supervillain but it is fully co-op. The other great thing about this game if that you are literally creating you hero as you play the game, which makes the theme feel amazing primary. Core Worlds is a fantastic deck build revolving around taking planets and moving through the galaxy to the core worlds. As you travel through the galaxy you open up new and better cards to buy. Core Worlds is fully competitive and very strategic. Star Realms is a very fun game with a nice sci-fi theme. It is akin to Magic the Gathering became you are attacking authority (the equivalent of life points) but you are building you deck as you play.
A few of the other games like Mage Knight and Sentinels of the Multiverse are not truly deckbuilders. Mage Knight does have a deckbuilding mechanic but it is defiantly not a primary part of any game if Mage Knight I have ever played. Sentinels of the Multiverse I’d an amazing superhero game but it had pre-made non-modifiable decks, so there is no deck build St all.
When trying to choose a starting deck builder I think it is very important that to know what you look for in a game. If you are looking for theme you may want to choose something like Arctic Scavengers or Heroes of Metro City. If you really like mechanical interaction Cryptozoic games or Dominion style games are definitely where you wanna start. Good luck with choosing a game everyone!