Think Flash Duel is a great game also. Played it a lot with random strangers or friends over the years, and it was almost universally well received no matter the edition. Unfortunately each edition has had some pretty serious balance problems.
1st Edition - Deck runs out quickly and it is hard to actually kill someone; gameplay usually begins with playing footsies to get hints on what your opponent's hand is like and positioning yourself to get first Dashing Strike (and being able to continue the pressure) or blocking the first dashing strike. The winning strategy is to set yourself up so you have control over the last move (or checkmate your opponent so that they have no good last moves) so you will win by last hits or distance.
Setsuki is the best character in First Edition, and was toned down for Second Edition.
2nd Edition - Strategy is the same as First Edition, but there are new characters and balance changes.
Quince and Setsuki are the most powerful characters in Second Edition. IMO Quince was really fun to use though.
2nd Edition Revised - System changes to make more cards in the deck and make the deck less predictable for more bluffing and risk taking etc. There are no more last hits, but it is still hard for most characters to kill the other without cornering them so the main strategy is to set up good enough offense to corner the opponent or just win by distance. So the strategy is similar to 1st and 2nd Edition, but the longer round means there is more time for the player with initiative to run out of steam and the player with his back to the wall to find a weak spot and make a comeback which makes the rounds more exciting.
As a result of the system changes, best character in 2ER is Argagarg, who has a completely dominant matchup against the vast majority of the cast -- because winning at timeout is still so important but last hits no longer pose a threat, his Pacifism will automatically win a lot of rounds or force opponent into making bad or risky moves to try and actually kill him, especially when you factor in his defensive abilities. Some characters can kill him but most simply can't really without abilities tuned for the task.
From a gameplay and overall balance standpoint, I think each edition got significantly better, though I think Argagarg in 2ER is unfortunate since I'm guessing it will be the last iteration of the game.
2v2 in 2E was very fun, but the endgame situations were way too complicated which reduced its playability to me. 2v2 in the Revised 2nd edition is probably a lot better though! Didn't get the chance to try it much.