Discovering a hidden weapon in a game is an amazing feeling, or finding a new treasure that challenged your skill or ingenuity. I didn't get many of those voila moments in Oblivion, but Morrowind was full of them.
This is very true. One of the few voila moments that I can still remember was finding an enchanted staff at the bottom of the frozen lake in Solstheim. I was so happy when I found it; maybe the staff was useless and not very powerful but I was so happy when I found it. Also, I didn't know about the quest to get the robe of woe in the well at the back of the Skaal village. Rather, I had been adventuring and found a note left by another enemy in another cave. I think it was a journal-entry. I read it and at the end he said that he really wanted the robe of woe, and mentioned where I could find the owner.
I was interested so I went looking for the cave for ages, but finally found it and made my way to the person wearing the robe and killed him; I was SO happy when I got it. I made a huge post about it on GameBanshee but no one seemed as excited as I was unfortunately. I was so amazed to find something that was so powerful and unique while not expecting anything, roaming caves in the wilderness.
This is a feeling I hope to find again in Skyrim; I never had it in Oblivion.
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I'm a little nervous about the whole shop-owning mechanic since it just gives me a bad flashback to Fable, which I didn't enjoy at all. But this is just opinion. What I liked about Morrowind and Oblivion is the 'nomadic' lifestyle that your character can live. While yes, the feature can be in and I can just choose to play without using it, but I wouldn't like it shoved in my face all the time. Like Jonquil said, I would like things to be much more subtle, more subtle than things were in Oblivion. This gives you this feeling of wealth and depth for the game.
One of things I do remember is that when I heard Morrowind was coming out I was so excited that once the game was out and everything, I printed out walkthrough to all the guilds and things. I read them like novels. I didn't experience the majority of quests 'blind'. This I truly regret, but there was so much more to Morrowind that it didn't matter. I could still play and find new things to do. Not so with Oblivion.
I hope that if they do implement voice-acting (which they probably will), that there's more than just a variety of one-liners.
/off-topic tangent