The Elder Scrolls: Arena was, eventually, a far more successful open-ended game than Darklands, though it was likewise somewhat more buggy than it should have been upon its release. However, it ended up spawning one of the longest-running RPG series to survive past the early 2000's, with four games in The Elder Scrolls main series as well as a several expansions and spinoffs.
Part of the reason for Arena's success was its effective use of modern game technology. It is built off of the Ultima Underworld model, but in many ways surpasses even that classic. For example, melee combat in previous 3D games was accomplished by clicking and holding down the right mouse button, with different attacks corresponding to different clicking locations, like a slash if you clicked from the right or left side of the screen. In Arena, on the other hand, melee attacks are accomplished by clicking the right mouse button and moving the mouse in the direction of the attack, which your weapon follows. The whole process is much more visceral and immersive, and makes the action in the game feel much more like action should. Likewise, the superb sound in the game adds to its appeal - hits land with satisfying thumps.
Arena's huge game world is also a major draw. Unlike its predecessors, travel around town is not accomplished via text menu, but rather, each town exists in its own space, and you can wander and explore throughout, from small villages to major metropolises. You can also wander in the outdoors between towns, but it is not an effective mode of travel. The game world is also filled with books which fill in the history and geography. Some days are holidays, with effects like cheaper magical items or free blessings in temples. There is something magical in Arena and it shows up best when you wander into a new town, discover that it's a major holiday as the snow falls and the game's evocative music plays.
These moments of beauty only really occur in games with huge worlds that put the player in small but important positions, as opposed to building the entire game world around the player's quest. Later Massively Multiplayer RPGs like World of Warcraft could achieve similar effects. The Elder Scrolls series is, in some ways, a predecessor to those MMRPGs, and later games in the series would often be described as “single-player MMRPGs.”
Arena is also creative in ways that many RPGs were not. It offered a spell creation system, which a magic-using character could use by combining the effects of different spells. For example, you could build a spell which caused both paralysis and poison. Its sheer amount of randomized dungeons and semi-randomized quests could keep you busy for weeks without ever having to worry about the main plot, although the simple fetch and escort quests could lose their charm.
Of all the great RPGs of the early 1990's it's something of a surprise that The Elder Scrolls: Arena ended up being the one with the most longevity. Its embrace of new technology and creative ambition certainly made it stand out, and subsequent games have demonstrated its creators' ability to adapt to different technological and business environments. Its first sequel, Daggerfall, surpassed it in most respects, but it's still an eminently playable game on its own.