Was totally going to post Waves by The Dear Hunter, but you already had it
That is a perfect example of a song that I could see becoming a mainstream hit. I could see it appealing to the masses and most people enjoying it. It is my go to song when I try to get friends and family, who only listen pop chart music, into music with a bit more depth and ambition.
I find the biggest problem with people who only listen to the radio, or what's in the charts, is that they seem incapable of making their own mind up about if they like a song. If it gets forced down their throats, via the radio, they know it's 'popular' and know it's ok to like it. They generally also only want a quick fix and then move onto the next 'hit' single and play that to oblivion. That's a whole other debate. I don't mean to generalise the casual music listener but that's my experience.
Yeah, I'm sorry to be the contrarian, but I don't believe that at all. Yeah, some of those songs get play because they're by "Artist X", not purely on their merits, and yeah, I know there is some science to the idea that "repetition works", but the list of bands that have crashed with a bad song as a follow up to a hit is as long as my arm. I think that generally - not always, but generally - the songs that are hits are hits for a reason. This idea that "everyone would LOVE Tales From Topographic Oceans if they only heard it!" (and I'm being facetious here) is really nonsense. It's not like Marillion is releasing songs into the ether. They sent these songs to radio. They MADE the charts by brute force, but people heard the songs and didn't respond.
And as for the people who listen to the radio, well, that's my wife and my daughter. I don't at all consider them people that "can't make up their mind". They actually LIKE that music. Believe me, they've heard their share of Transatlantic and DT and Marillion and Genesis... which sort of proves my point; how many people got into Genesis with "That's All" (one of my least favorite songs ever) and heard "Dance on a Volcano", and rather than saying "Holy shit that's so much better than the crap they're doing now" ACTUALLY said "Time for a BEER!". Why do you think their setlists were predominantly post-Abacab?
Honestly, "Dry Land" was as big a hit as it should have been.
Having said all that, in the spirit of the game, I would put "Kayla" by Flying Colors here.