I think the whole, "Ness players think Ness is bottom 5" thing died in 3.5. I don't think any top level Ness players have said that he was bad in recent times, unless it was just a joke. I don't think Ness is amazing, I don't even think he's great. I think he's solidly high-mid tier. Right around the ~20 range.
The big problem with Ness is that he loses hard to two things: circle camping and large disjoint. His losing match ups are top and high tier characters like Fox, Wolf, ZSS, MK, Marth, Tink, Sheik, Falcon, and Peach. He does have the tools to reasonably compete against those characters, but it's still an uphill battle.
Take a look at Fox, ZSS, and Tink, for example. These characters are much more mobile and have spammable projectiles. If you didn't see my WF set against Lunchables from IAB, check it out. Game two, he picks Tink and runs away, camping me out the entire time. It's extremely difficult to deal with. Take a look at reslived vs. Aidan (ZSS) from Blacklisted 2. Aidan runs away, camping him out the entire time. That is the optimal way to play the MU. When it is played that way, it feels virtually unwinnable. So, in theory, these match ups are horrible, but theory and practice are very different. In practice, they are doable, because no one seems to be able to camp forever (Hax vs. Plup, Evo), or once a hole in the strategy is figured out, the camper either abandons their plan, or fails to adapt.
I think that if everyone plays the MU the way Lunchables played against Stereo, it would be a lot less likely that Ness players advance TOO far in bracket.
And for what it's worth, no Ness has been in top 8 of an EC tournament since SF2, where res got 7th after a solid, but not particularly amazing bracket run. Prior to that, I believe the last time a Ness was in top 8 was when I got 5th at the TLOC 1k, which wasn't a major, and before that, Final Boss. At Supernova, res got 33rd, and Stereo and I each got 17th. At Blacklisted 2, I got 9th, res got 13th. Aki got 2nd at NWM, but that was basically him just playing in his region. I don't think Ness' results are as impressive as everyone lets on. Good, yes, but top 8 every tourney, no. Unless I'm missing something.
tl;dr: Ness is probably around 20th in the game, has a hard time with top tiers when they play campy. In practice, it's not as bad, since not many people play that way, or if they do, they don't play it effectively.