25/50 for me and am very surprised that I am 'ahead' of drron whom I had imagined to be extremely well travelled. My guess was he would have seen at least 33/50.
These lists are extremely subjective. No one will ever agree. Omitting Hong Kong, Moscow, St Petersburg and Shanghai is extremely questionable (I've been to all these and would rank Shanghai way ahead of Beijing, though perhaps that shows a Westerner's bias) while Seoul, Manila and Jakarta were also off the list. The last two aren't scenic as such but they both have important history (such as how Manila was second only to Warsaw in buildings obliterated during World War II if I recall, but still has Intramuros) and are major, 'mega size' population centres (and increasingly notable for economic growth or in Manila's case rocketing up in the tertiary - service industry - sector). Seoul is an incredible example of a non Japanese 'connected city' in terms of communications and has advanced hugely since the Korean War.
Another plug for Melbourne: we are on the way to being Australia's largest city and while we lack an Opera House or Harbour, the laneway dining is something that many cities (e.g. Sydney) would like or seek to emulate.
Weren't Vancouver and Toronto, Canada also omissions? I've been to the first, which was great. Boston USA, while small in resident numbers, has great history and atmosphere. La Paz, Bolivia is also a most unusual place and well worth inclusion given its most unusual setting.
Krakow, Poland also didn't make it, yet it's on many individuals' wishlist and an enjoyable and historical place to visit.