The Elder Scrolls III: Bloodmoon

Both Bloodmoon and Tribunal, add-ons for still-popular Morrowind, each have their own distinct flavor that borders on experimentation. While Tribunal tries out things like pack animals, hirelings, reliable armor construction, and a place to dump some of your more famous artifacts, Bloodmoon's radical landscape differences is a straight up a vacation from Morrowind. Sure, there are some pretty epic magical items hidden away there, and it has its own limited armor construction system, and Bloodmoon tries its own innovations by allowing the player to make choices that actually have a permanent effect on the environment (however minor those effects may be), but one of the primary impressions is one of difference.
 
All the monsters, trees, landforms, and most of the underground locations are chiseled from new molds. Rather than being boxed in by volcanic mountains, the island of Solstheim is relatively wide open, with bears and wolves milling about, waiting to gnaw on a tourist or two. There are plenty of regenerating human enemies too, with fryse hags firing deadly spells and reavers and berserkers trying to cut you a new one with axes and arrows. The herbological materials are pretty limited, but do allow an alchemist to make stuff that helps fight off the cold-heavy spell complement, and most of the items found in chests scale to level, but tend to have a much wider array of interesting and useful materials, rather than the usual cup-plate-bowl, spoon, and goldpiece you might usually find.
 
Weather is snowy, both gentle and blizzard, and there are clear sky days as well, all welcome sights when the ash storms and humidity take their toll. Caves of ice and barrows full of undead provide different targets to murder and loot, while there are four primary locations where you can get quests and make a few of those world-changing choices.
 
Nothing is quite as world changing as an option to become a werewolf a good way through the main quest, and there is an entire quest line for werewolves that allows the player to take an alternate path the the expansion's conclusion, working directly against the forces you would otherwise be allied with. Werewolves are a bit more enhanced than they were in Daggerfall, and admittedly it can be pretty fun running through the tundra, hunting down the single human kill you need to stay healthy and happy (you can kill bad guys, too, so it's not about griefing innocents necessarily). But ultimately this feels a bit like a minigame to indulge in, rather than an alternate lifestyle: the entire game world knows you're a werewolf instantly if you change in front of them, you can't access your inventory or spells until you change back at dawn, and the enhanced mobility will likely pale in comparison to a player character decked out with high level gear and magic. I found the werewolf section to be cathartic like playing a little Grand Theft Auto after a hard day, but actually deciding to play as a werewolf will demand a lot from the player.
 
The other choices don't have quite as much impact, but are still interesting to see in what feels to be a relatively static universe in Morrowind as a whole. The quests you follow to help build a mining colony result in a few permanent differences, both in ownership and in structures, and the quests in general seem to allow for the player to choose a bit more than the usual yes/no dynamic that Morrowind players are largely accustomed to. 
 
High points for me included being stuck in a blizzard standing on a high peak, almost feeling the chill of the wind, and making my way through an icy castle. Many of the quests had interesting subtexts that felt very noble and straightforward, another refreshing change from the mire, however satisfying that is, in Morrowind's tangled politics.  A few of the quests were especially well written, either edging toward humor, or approaching the stirring epic you'd expect from the Norse-inspired Nord culture.
 
The combat, though, can be a grind, and the usual problems of escorts taking on things too big for them is still an issue here. Going too early or poorly equipped can result in the PC being bashed six ways from Sunday, and much of the loot, while useful, may not fit in with your chosen weapon styles.  Some quests have a bit of that old ambiguity, and there is a hard quest that may actually require the player to load to prevent the loss of a useful main character, which is something that hearkens to games ten years ago, but seems a bit against type when compared to the other, less demanding quests in Bloodmoon and Morrowind as a whole. Probably the biggest disappointment, though, was how a lot of the choices made don't seem to amount to much. The soldier assigned to you to help root out a nest of smugglers is done with you one mission later, you can put a building right in the middle of a former trouble spot to no ill effect, and many of the quest choices run in parallel for both branches, which is fine the first time, but deadens replay value a bit compared to the completely different House and Guild quests from the main game.
 
It's hard to escape the "vacation" feel of Bloodmoon; the feel of its quests, the monsters, the loot, and especially the land, all feel so different as to act as a palate cleanser that clears away some of the ash from the main game. It allows for many interesting choices, even if they don't have much depth to them, and has tucked away some pretty powerful items that don't quite break the game but are certainly fun to have.  After doing a lot of the busy work required for the main quest (NOTE: some of these are especially aggravating at times with an inadequate paper and no way to mark several important spots on the in-game map, a bit more so than many of the main game's quests), though, the player may easily become exhausted with it. This is the perfect time to return to the wonderful and weird main game, with its strange sights and sounds.  Like with most vacations, it makes you appreciate home all the more, though you will miss the more varied conversation and mission choices when you return, as well as the more colorful characters.
 
Bloodmoon is not for low level characters, and it feels a bit flat for more powerful characters. If you're thinking of jaunting to Solstheim, best to do it from about level 10 onward. There's plenty of time to put in there, plenty of places to explore, but beware that the enemies can sometimes hit a bit harder than you might expect.  For those wanting to have a bit of a taste of what's coming up late this year in Skyrim, all I can say is that I have no idea what tone TES: V will try to maintain, and whether or not it will contain any reference to things you learn on this island. Rather than worry about its possible connections to Skyrim, though, you can enjoy its Nordness for its own sake, and if you find correlations with Skyrim later, then all the better.