I can imagine a handful of other arguments (including the possibility that the album is totally awesome and I am wrong) for its success.
This seems the most likely answer.
I would like to note that almost everyone here has failed to give a real argument about I&W being better than DT12. While I made this thread to appeal personal opinions, you can absolutely write down WHY you think it's the best one out of the two, yet everyone says because it's... I&W, alright, why? James Voice? I agree, James's voice was awesome, yet I think it was better at SFAM and Awake (Not fond of high voices).
- Technically, James's voice is better. He has that soaring majestic quality to his voice that a lot of people really enjoy and identify him with.
- Because it's their second album, it has a youth and vitality to it that most people generally enjoy in music. A band's earlier albums are going to be generally more liked because they take more risks and haven't worn off their rough edges. Especially in the case of I&W, DT was in the process of inventing a new genre of music and establishing its conventions.
- Pull Me Under is DT's one legitimate hit single. This shouldn't matter, but it does. It makes the song feel bigger and more exciting.
- MP's drumming is very unrestrained and intuitively musical. MM's drumming on DT12 is very precise and mechanical. Some people prefer the former, some people prefer the latter. (For me, I think the drumming on I&W is better overall, but the drumming on IT is better than any song on I&W).
- I&W's mix isnt nearly as compressed, which is nicer on the ear. While the bass mix on DT12 is very good, it's better on DT12.
- Myung's bass work on I&W overall is more inventive and unusual. This matters to some people.
- Overall, the guitar solos on I&W are better. They have the jazzy elements that eventually got pushed out of JP's soloing. And while DT12 has some soaring melodies, they feel more casually effortless on I&W.
- KM's keyboards, depending on how you look at it, are more atmospheric than JR's on DT12. And his keyboard solos tend to blend melody and the technical aspects more naturally.
- The biggest factor, I think, is that even though DT12 moves between many genres and styles, the whole album is very heavy and very dark music. Even AFTR has a very slamming mix and the darker bridge section. I&W goes from heavy metal to ballad in its first two tracks.
You don't have to agree with these reasons, but I&W isn't so well liked purely for nostalgia reasons. This isn't meant to diminish DT12 either. IT is better than anything on I&W (IMO!!!!!!) and the album as a whole is in my top 5.