Worst how? Let's see...
Camera is useless in poor lighting, M8 blows it away in low light
Touch wiz hogs ram like no other, stock android on N5 doesn't.
Feels like a plastic toy even compared to the N5 which is half the price
M8, Z3 and G3 have even better battery life
Touch wiz Lag... Shouldn't need to explain, all other flagships don't lag like touch wiz
There's a lot more. The S5 really doesn't do anything better than any of the other flagships, people buy it because Samsung spends way more money marketing it than any other android manufacturer.
I'll give you the first one, but if the S5 is useless, the the rest of them are poor, you're exaggerating. No smartphone takes good night shots.
Unless you're a vampire, the HTC M8 has a below average camera, the N5 is average, the Sony (Z2) are good but should be better.
The rest it just rubbish in my opinion.
My battery life is stellar, reviews back this up.
I don't have ram issues, I don't have lag issues, the feel is subjective, I always use a case anyway, let's see a tesla run any of the other phones and see how they handle it.
The one think that is poor is the speaker, but you never mentioned that. Makes me wonder if you've even used an S5, it's the worst thing about the phone.
So the worst? Nope. The best? When I purchased it, there wasn't much competition in my opinion. Then again, I'm not saying it's the best or the worst. You are.
Looks at how it compares to a new phone that's bring touted as the best.
http://youtu.be/oE8jHskLNfQ
Anyway, I disagree with you and I also think your just parroting what you've read and not talking from experience.