Probably The Whispered World.
I'd heard great things about it, so I went ahead and bought it on Steam. But the graphics were nowhere near as "gorgeous and painterly" as I'd heard, the art style and character designs were just kind of gross, the music was forgettable, the characters were obnoxious as fuck (especially the protagonist who had the most annoying voice I'd ever heard, to the point that every time he talked I had to skim the subtitles and then quickly press spacebar), every attempt at humor made me cringe ("pantaloons" is not inherently funny, stop expecting me to laugh just because you said it), and to top it all off, it had an "it was all a dream" ending with a glurgy sick child aspect tacked on to tug at the heartstrings or whatever.
As to the gameplay, there was one thing about it that I liked: the main character's pet slug could take different forms (normal, fat, on fire, etc.) and you could use him in all those forms to solve puzzles. But the rest of the gameplay just embodies all the worst parts of adventure games: tedious grocery list dialogue, and puzzles that consist of throwing everything in your inventory at a problem and, when that fails, trying to stick it all together and then throwing it at your problem.
Some of the solutions made sense, but in one case I had a turtle statue that I learned, through trial and error, I could stick a bunch of crap onto, including a pair of dentures. I had no idea what I was supposed to do with the resultant monstrosity. Turns out I was supposed to show it to someone so they'd get scared and hide and I could enter the door they had been standing in front of.
That annoying gameplay is the biggest reason I've never been able to get into pure adventure games, even the classics like The Longest Journey. For me to enjoy an adventure game, it has to be puzzle-adventure (the Myst series and Machinarium) or action-adventure (Ico and Aquaria), or even just exploration (Journey and Botanicula). Those are all among my favorite games. I love most subgenres of adventure, but adventure games themselves, when they rely on inventory-based puzzles and spending hours going down dialogue lists, really don't do it for me.