Arena was drab and dull, but you weren't fighting the demon apocalypse...
You were fighting to save the kingdom from the rule of one of the Emperor's most trusted advisors, who had betrayed him and taken his place as ruler. To beat him, you have to travel to eight uniquely themed dungeons scattered across the world to find the pieces of a MacGuffin, the only item powerful enough to defeat him. On doing so, you need to go to the palace and use its power to defeat him, thus destroying Tharn and bringing everything back to exactly the way it was before.
Let's set aside the fact that "advisor betrays emperor and takes his place, lowly nobody has to stop him" is an astoundingly old plot and one that's arguably more common than "demons are escaping from hell, drive them back". Let's also ignore the fact that you represented Oblivion's plot as "save the world from demons", which is a decent enough description of the basic plot, but Arena's plot as "save the emperor, because he was betrayed", which is a bit of a side point to the actual plot (which is "save the world from pure evil villain"). Hell, let's even ignore the fact that technically,
you aren't the one saving the world from demons in Oblivion. Even with all that aside, there's
no comparing Oblivion to Arena in terms of clichés. Oblivion's plot is fairly unoriginal but has a few major departures from your prototypical fantasy story, while
Arena's plot is your prototypical fantasy story. Arena's main quest (again, eight dungeons with each a piece of an ancient relic that can defeat the powerful evil you're facing), its villain (Mehrunes Dagon is a being whose very essence drives him to wanting the destruction of all things, Jagar Tharn is evil
just because he is), even its world (a very standard high fantasy setting), visual design (Oblivion at least has the Ayelid ruins and occasional roman influences, whereas Arena is high fantasy right through), and most of its
gameplay (Arena's stat system, races, and actually most everything about it is lifted
directly from earlier versions of D&D, the absolute basis for every fantasy RPG, and changed only just enough to avoid a lawsuit... and I do mean lifted directly, given that Arena is based on the D&D sessions its developers used to have) are all literally entirely clichéd, without a shred of originality about them. I like Arena more than I like Oblivion, but while Oblivion has a lot of unoriginal elements Arena is one of the most wholly unoriginal RPGs I've ever played, bar none.
If you don't like Oblivion then that's fine, but don't exaggerate how bad it is or how good the older games are just as an excuse to rip into it. Claiming that Oblivion's story (or really, most anything about Oblivion) is more clichéd than Arena's is like claiming that eating a hamburger in one sitting is more unhealthy than eating twenty pounds of raw ground beef in one sitting - the two just aren't on the same level at all.
Diablo 2 if one were to look at as an "action" RPG. Hell, the portal in Oblivion and the portal in the expansion pack of Diablo 2 looks so similar. We could even use Tyrael in the place of Sean Bean, up to the point they both become the big hero in the end.
Except Tyrael isn't the big hero the entire way through. I wouldn't even say he's a hero in any of it, until the very end of the
expansion (and even then I still wouldn't go anywhere near that far). He plays a supporting role in the overall story, while the character you play is
far more important to very nearly everything involved.
Oblivion is very different. Martin is the main character. Not a supporting character but
the most important character in the story. The comparison to Diablo 2 really doesn't work, because you're saying "well, Tyrael was kind of important at the end" and saying that makes him equivalent to a character who was clearly the most significant one in a story right from its very beginning.
The Cliche part of the whole thing is Good vs Evil and Demon Invading X place. The Delivery Boy is usually a given in any RPG.
Again, you're stretching things. "Delivery boy" is a given in any RPG in that you're expected to go doing fetch/delivery quests. That's not the kind of delivery boy we're talking about here. We're talking about the character you play as being a delivery boy for the
actual, main hero of the story. The fact that the rest of the plot is very clichéd doesn't make that any less original.
But usually on the line that Morrowind would go with the theme of "Chosen One" but it is own, weird way.
The only especially original way it goes about it is the point about the reincarnation business actually being untrue, but even that it undermines a lot nearer to the end when a lot of the dialogue and events
really tilt things in favor of all the babble about Lord Nerevar and prophecies being entirely true and accurate (especially when you go screw up the Tribunal afterwards).
Morrowind made it unique. Your foes weren't "EVILDEMONZ!!!11!1"
Except that most of them were, with the exception of Dagoth Ur. There's not a single antagonistic character in that game who's in any way sympathetic or good except Dagoth Ur, and Dagoth Ur's motivations don't change the fact that what he was doing (spreading blight to innocent people) was just undeniably bad in pretty much every possible way.
Off of that, I feel that it should be pointed out that http://www.cold-moon.com/images/Motivators/Alignments/GoodVsEvil.jpg.
This is the main point, and this is what I'm trying to make people understand.
Every game in this series is unashamedly clichéd and absolutely stuffed to the brim with entirely unoriginal content. No exceptions. None. Except maybe Battlespire... maybe. Some of them (Morrowind and Daggerfall) develop a lot of their unoriginal content more than others (Oblivion and Arena). That does not make them stop being unoriginal, it only means that they put more explanation into the ideas they've taken. It doesn't matter, because (except in Arena's case, where we're talking about the absolute extreme)
a game doing something that's been done before, taken alone, shouldn't be a criticism. Ever. EVER.A lot of games lift a lot of ideas from a lot of places. They lift those ideas because
those ideas work. The concern should be over how well the individual games handle and develop what they do have,
not where what they have came from.