I don't know of any competitive player that would think skill gaps are bad. Skill gaps are what make the game competitive in the first place and give players something to achieve. It means that the game rewards players that put time into the game. Games with low skill gap (or none at all) usually aren't very great competitively and don't enjoy the longevity that games with skill gaps do. Most of the time players buy the game, play it for a bit, then put it on the shelf to collect dust. Skill gaps are good for gaming, and it doesn't mean that casuals can't enjoy the game too. They just need to realize that they need to practice some to be on the same level as those that have surpassed the skill gaps. I mean, how do you think players and fans would react if the changed the rules of baseball so that anyone can play? Change it from a bat to a flat board, change the ball to a tennis ball, move the bases closer together and give everyone 20 strikes before they are out. A baseball game like that would have virtually no skill gap and fall apart under the weight of its own inadequacies. Catering to casuals is what is destroying gaming right now because everyone wants to be good but no one wants to put effort into being good. They just want it handed to them. Sorry I don't buy into that mentality. If you want casuals to enjoy the game put in stuff that can enjoy, which is where stuff like SSE, items, and crazy stages like Big Blue come in. They are wacky and give casuals something to do. But when it comes down to true player versus player, if you don't reward the better player people will get fed up with the BS and move on.
I know what you're saying and I don't agree. You take input from players when your vision and their vision are on the same path. But the moment your vision contradicts theirs you will end up alienating veteran players, essentially starting over with as if it were a new game. Case and point, Gears of War 2. In Gears 2, Epic tried to FORCE players into their vision of the game, tactical cover to cover fighting, by changing a lot about the game. It was generally met with a very poor response from the core fanbase and a lot of players quit playing. They put out updates to change some things here and there so that the game would be more of a balance of cover to cover tactics and close range gladiator type combat (with the Gnasher shotgun). In Gears 3 Epic finally embraced the player's vision of the game, but still managed to keep part of their vision alive too. The end result was the best game in the franchise. Then Judgement comes out and Epic gave players some of what they wanted (eg. no stopping power), yet AGAIN made unnecessary changes to core mechanics which just ended up destroying the game. Sure there are fans for all 4 games (I personally enjoyed 1, 2 and 3 all the same), but Gears 3 was the best selling, has the most players playing online (current average after 2 years is about 7k for versus, peaked probably saw upwards of 20k, IIRC it has been in the top 20 for XBL since it came out), and it generally considered the best version of the game. That's because it embraced the player's vision of the game. Granted there are some flaws, but most they are minor ones really.
Also IDK about LAN's as much for these games, it really is only online. I mean, why bother bringing your 360 and a TV to a friends when you can just go online and play together? Don't get me wrong, smashfests are great but they would be 1000 times better if you could do it online from the comfort of your own home. This is getting into another issue I have with Nintendo, that being the very poor quality of online play. It is 2013, stuff like voice chat, online lobbies, and party systems should be standard. Apple's iPhone does online play better than Nintendo.
Actually US SMB2 is not a very beloved game. Nintendo had their head up their own *** when they did that one, because when they went back to the more difficult but more traditional style of Mario in SMB3 everyone loved it. SMB2 is only a classic in the same way that Wind Waker is or any the other games you mention; nostalgia makes the heart grow fonder. There will always be players who enjoy one particular game over another. SMB2 was a great game, but not a great MARIO game. In fact, as a Mario game it is downright horrible. No power ups, very poor platforming mechanics, really bizarre health system, and unrecognizable enemies (for the time). Then when they went back to the old style in 3 and World for SNES they were considered masterpieces of Mario games. They did what Mario games should do, they focused on the core mechanics that made the original so awesome and then improved on that. Then 64 comes out and Nintendo does the unthinkable, putting those mechanics in 3-D. But again, a masterpiece because they followed the formula. But then Sunshine comes out and suddenly people don't like it. Why? Because it moved away from the formula and tried to become a different game. Seeing this, Nintendo went back to formula for Galaxy and it was an excellent game, though a bit gimmicky with the controller, but still my point is that moving away from what made the originals so good is how you make a bad sequel.
Again, SMB2 was a fun game, it just wasn't a MARIO game. You say it was the "right" decision, well you are wrong, because Nintendo went back to Super Mario 1 for pretty much the next 3 games and they were all far more successful than SMB2 ever was.