Two can be as bad as one
Of course, that's not a great sample, since I wouldn't know a Syd Barrett song if the refrain were "This is that Syd Barrett song you're supposed to know." Not to speak ill of the dead - if he was an innovator, let him be remembered for it - but early Pink Floyd struck me as pompous and meandering, and pretty much all the same.
Well, wait, that's not quite it either. I'm pretty cool on later Floyd too. The Wall has some good bits, but art that whiny and narcissistic should be on a controlled substances list with "Freebird" and Catcher in the Rye and only distributed to people who have moved out of their parents' houses and gotten full-time jobs. Dark Side of the Moon is good, I guess, but redundant if you've got a copy of Wish You Were Here.
Which brings me around to my point. Everybody knows what a "one-hit wonder" is. What should we call its opposite: that act which keeps notching hits with, as near as you can tell, are the same damn song again? Whose Greatest Hits album should be one side of a single?
Alison and I call this the "all you need" game. For example, I contend that Back in Black is all the AC/DC you need. Now, Back in Black is an awesome song, but if AC/DC actually recorded two different compositions, it's news to me.
Or consider Jimmy Buffett. He's got two songs: the fast one and the slow one. But English-speaking people have been writing sappyass nautical ballads for four or five hundred years, and "Son of a Son of a Sailor" doesn't quite measure up. So, pick the best of the fast ones, and once you've got a copy of "Cheeseburger in Paradise," you've got all the Jimmy Buffett you need.
If you want to get ambitious, you can go for the multi-band combo. "Kryptonite" by 3 Doors Down is not only all of them you need, but also all you need of Nickelback, and possibly Train and/or Creed. Don't let encroaching fogeyism tempt you to overreach, though: Marilyn Manson stole his image from Alice Cooper, but they don't actually sound much alike.
You can defend, of course, by pointing out at least one substantially different song by the artist. Sure, ZZ Top has been putting retreads on "Legs" for about 20 years... but one of them isn't enough because you also need a copy of "La Grange." And yes, you do too need both.
By now, I should've either slighted a band you like or left out a band which you just know needs a good trashing. So air your grievances in the comments...