Well, my experience has been different. Ive only dabbled in other games but here were my experiences.
Gwent: I kinda hated it. I felt like I was bringing a rusty butterknife to a gunfight really quickly. In other words felt like I was bringing a starter deck vs tier 1 decks almost as soon as I left the tutorial.
Mtg: this seemed pretty good, but it was a little daunting to try and figure out how to get a good deck built. I feel like if I had started with this game it would have been a good choice though.
Eternal: I thought Eternal had the best execution for gameplay of all the ones I tried. Combat was lively, but managed more depth than Hearthstone. Unfortunately, I got bored of the cards pretty quickly. Maybe simple cards helped with the gameplay, or maybe I just didnt stick with it long enough, but if there is ever a Hearthstone 2 they should steal heavily from Eternal IMHO.
Runeterra: I couldnt get used to the turn system. I constantly was not knowing what was going on. This is probably a temporary thing, like not being able to figure out what taunt does, but it was an exit point for me.
Hex: now defunct, but had by far the best pve experience out there. I wish Hearthstone would steal that.
There were a few more that had nice things to offer. More often than not I just found the cards to be booring in comparison to Hearthstone.
Answer is in the name of the genre- CCG: Collectible. Personally the reason I like Hearthstone the best is because I’ve played so long that I can play whatever deck I want for free with all the saved up dust I have. I only play standard and have only 1 wild deck for flavor. Classic is meh. I also love the cartoonish design, but I will give props to runeterra. That is some immersive art and I do think in time it could take the lead over other CCGs. HS has been such a flagship that it’s going to take a while for others to gain the level of popularity HS had at its peak.
I don't particularly love any digital card game currently out. I don't care about ftp friendly, as I just prefer buying expansions anyways, such that you get every card (Without having to worry about random packs). Examples of this done in physical games are things like the netrunner LCG by FFG. I tried the LOTR ACG, (basically the same company trying to reach into the digital space, but there wasn't enough build around cards or synergistic cards for me to really be satisfied. Other than distribution methods, HS is probably the game I like best currently out in terms of mechanics. It's honestly really frustrating for me. (I admit, I've not tried Legends of Runeterra, but I refuse to install anything made by Tencent)