As someone who just got back from the games last night, let me tell you my thoughts on the failures:
1) No one spoke English. This is a big one. I have done loads of international travel, and have never been anywhere where less people spoke English. I am talking about not even speaking a single word and just 2 years after the World Cup. I got by in my broken Portuñol (I speak Spanish and French very fluently), but I felt especially bad for visitors from places like Asia that have zero Latin language background to rely on.
2) Stadiums were a facade. On the inside they looked spectacular, in fact they are among the nicest looking facilities I have ever seen, but step outside to go to the bathroom the walls and tiles were coming apart. The plumbing is so bad that they made you dump your toilet paper in a bin rather than flush it (gross), and the connected faucets in many times weren't finished and basically just hanging out of a hole in the wall. Several of them were never even opened. The Track was a one time use, but it barely survived the week of operation.
3) Athlete security. The police did a great job keeping the tourists "safe", although there methods would generate all kinds of lawsuits. They were openly discriminating against any "seedy" looking individuals, not allowing them on certain metros, near the beach, and other touristy areas. That said, there was no special attention given to athletes, who had very little assistance with navigation and transportation. As most were wearing their credentials around town it was pretty alarming that nothing happened. More so, in the track for example, the athlete exit included a 50m jaunt through open stadium to the transport without protection. I could have easily just tackled Mo Farah in between his semis - and in fact the only athlete that I saw skip this route was Bolt. Great for fans looking to grab autographs, but awful for the athletes.
4) Stadium food was awful. When I saw awful, I cannot understate it. Not only was it totally disgusting, but there wasn't enough of it and most of the time you would wait in line just to find out that the only thing left was potato chips. At the football stadium they stopped serving all concessions at 70 minutes, even though the final went into penalties. Logistically they did a poor job in general, not even having the souvenir cups for several afternoon sessions.
5) Hot water at athletes village. I didn't spend any time there, but my friends competing said that they were taking lukewarm showers at best.
6) Public transit / venue location. One of my biggest gripes was getting to and from the venues. Everyone was staying in Copa/Ipanema/Botafogo, as a central location between the park to the west and the stadiums to the north, but most of the time it took between an hour to an hour and a half to arrive at these venues from the first metro stop. I tried taking an uber back from the park (which was only possible from a designated area 2km from the actual exit) and it took me over 2 hours to get through traffic. The metros themselves were designed to separate tourists from locals, but they were insanely overcrowded, consistently late, and a pain in the ass overall. I spent more equal time in transit and at events, which is simply inexcusable.
7) Tickets and empty stadiums. I had to pay ridiculous amounts of cash to get tickets from the States and did so because in London scalping was nearly impossible. However, upon arrival there were scalpers everywhere, and the only night I saw the track over 50% capacity was on Thursday for Bolt's 200 final. In fact the only events that ever sold out were ones that Brazil was in, as Brazilians could get tickets for insanely cheap compared to the rest of the world. From what I understand, they allocated tickets equally to continents which was clearly a mistake.
I have never been to an Olympics before, but I have been to the World Cup in South Africa and also the recent Pan Ams in Canada. Based on the above I would Rio a C+ overall, passing but only because there wasn't any major incident. All of that said, Rio in General is fantastic and the vibe overall was sick. Good, cheap food and drinks, beautiful women, clean beautiful beaches and views, and parties all night. It was a fantastic trip for me, but a pretty mediocre games in terms of preparation.