I stopped going to McDonalds around 2004 after seeing Super-Size Me (which didn't really convince me of anything other than what I already knew; Fast food in general is gross).
A few years later, I was hanging out with some friends and someone wanted a drink or something, so we walked in, and the smell was overwhelming, and disgusting. It wasn't different, it was the exact same McDonalds smell, it was just gross as fuck.
About a decade after that, I was dating someone who wanted some of their fries (they were having a bad day and wanted comfort food). So I drive over there, just order the fries (everything else she wanted was already at home), and head home. The entire time, my car was filling with this gross, oily, I-don't-know-what smell of those fries. It occurs to me that I could only define it as "smelling like McDonalds".
Mind you, I've gotten fries at Wendy's, Jack in the Box, Arby's, etc. None of them smell gross. They smell like salty potatoes (except any place that has curly fries; they all seem to be from the same supplier, and they're gross).
I haven't been back to McDonalds in probably another 10 years, but I can only imagine that my first reaction would be to wretch, and my second reaction would be to leave. I have no idea how they fucked things up so bad, I had them all the time as a kid. I still eat Wendy's spicy chicken sandwiches, they're fine. wtf.