I usually jump between Guild Wars 2 and the Elder Scrolls Online myself. But Warframe has been on the side of them as well since forever, but its more of MMO lite.

GW2 is very nice when it comes to combat and such, even if the large world events aren't really my cup of tea as the FX gets pretty bad. The story is decent enough and there is no subscription option at all. You do however need to buy the expansions and the living world story to get the entire game, i think there is a "complete pack" on steam. But its free to play the base game even though free accounts are very limited and should be seen more as an endless trial.

ESO has a far better world and deeper lore than GW2 does but i find its combat to be especially awful. A subscription is practically mandatory if you want to do crafting as there are a /lot/ of crafting materials and not a lot of inventory space. With the subscription you get access to the crafting bag which is just unlimited storage for crafting materials. The subscription also gives you access to all the episodes and expansions apart from the latest one. The story is often good, but nothing too exceptional.

Warframe is completely different as its a third person shooter. Its got some of the best movement in the business imo. Its entirely free to play as well with ways to earns everything in game, including the premium currency as its tradable between players. Its got some of the wildest lore of any game ive played and as such is quite unique in its take on sci fi. The story is great, but relatively short. If you do give this one a shot and hate the gameplay its not going to be for you as there is a lot of grind. But if you want to play a space ninja/walking WMD bouncing off of the walls while murdering hordes of enemies its definitely worth a try.