Considering the epic failure of so many other d2 like games in the past (even including some worked on by past employees of blizzard) I thought Torchlight did amazingly well. There are certainly many ways it could be improved but compared to the original diablo in scale at least I thought it was quite enjoyable. I still retained many of the fun aspects of D2, had better more current graphics and was much cheaper (also allowed very easy mod support!)
I remember reading that Torchlight 3 may actually be released before Diablo 3 and if that is true, and it does happen, it could allow Runic to seriously gather alot of fans....at least if the game continues to evolve a decent amount through each incarnation.
At the same time there are some negative signs I see as well. If Runic is already working on Torchlight 3, or plans on doing so right away after releasing Torchlight 2, that means there will probably be no expansion pack for the second version that adds more classes etc. In a way to me that is like giving up on a game before you have even released it and saying "It will not be good enough, we need to make another version." before audiences have even had a chance to play it, make comments and suggestions and hopefully want to play it more.
I remember hearing a Torchlight MMO might be in the works as well.....which is interesting. A great way for Torchlight to really blow away Diablo is to increase the multiplayer aspect beyond what D2 could offer. In many ways Torchlight fell short of the game D2 was even before the expansion pack even though it was released so many years later by people who worked on the original. It's a fun game but a casual one while D2 even pre-expansion was basically an addiction for way to many people. No ladders and multiplayer is probably a big part of that but just allowing a drop in/drop out multiplayer mode is not going to solve that problem. I was never a big dueling player but it certainly helped create a D2 economy and helped keep the game current. I think Diablo 2 would still have been an extremely popular game without the expansion but it was, in my opinion, the expansion and later patches that really pushed it over the edge into the realms of unprecedented popularity.
The first Diablo was a great game that I played many times, but I doubt I played it over 200 hours all together. The second game has the title of most played by me and many of my friends over the years and is still played by many even now. I hope Torchlight evolves much like Diablo did and I would rather see a higher price tag then just an updated version of Torchlight with a few minor improvements and multiplayer.
The game needs more diversity between characters, especially if multiplayer is going to be available now. While you could play each character in different ways, they all played extremely similarly. I loved the customization of characters in D2 and created many guides and character builds over the years (more then 20 I'm sure) that was the fun for me. In torchlight there wasn't the same ability to create your own character....and I am certainly not talking about how it looks.
So I agree with an above poster. T2 needs to seriously improve it's skill system, item drop and gem system and hopefully include runes of some type or something that makes you work long term for very powerful items (other then heirlooms). A leveling system of some kind for your pet would be nice or at least some other options besides the spells you add (more along the lines of hirelings in D2 for instance...but honestly why just clone....improve and make pets into a full fledged customizable character as well, with pet skills, stats etc).
Imagine having not only the ability to PvP or battle in an arena, but having the ability to set your pets to fight each other while the players watch. That could be seriously fun. Maybe even include the ability to place small bets on the pets hehe.
Torchlight has great potential because it has already grabbed the attention of a large audience. I hope it uses this opportunity to not just fix many of the complaints about the first game (adding multiplayer, fixing identify/item drops etc) but to surpass D2 in as many ways as possible. I love D2 and have played it to death but it is way past time for another game to take the reigns. Sacred, Titan quest etc have all to a large extent created a similar gameplay (and in many ways superior) to what we saw in Torchlight (although at a higher price tag). Torchlight 2 needs to separate itself from the pack and hopefully blow that tired old game (Decard Cain may actually be younger then some of the initial d2 players now) out of the water.