This was not an easy one to decide. Even within the past hour before writing this, I changed my mind at least three times (and may do so again). But after long deliberation, I have to go with Tbilisi. While it's true I have had some of the best nights out of my life in Dublin and have never seen anything like Krakow after dark, Tbilisi is without a doubt the most unique and inexpensive experience of the bunch, and (probably the tipping point) does not have the hordes of tourists. The other cities have great fantastic atmospheres at night, there is no doubt about it, but they all resemble, at least to an extent, what I am familiar with. When it comes to Tbilisi, I had no idea what to expect. It was like an exciting new discovery wherever I ended up going out, so in the end, it takes the cake as the best.
Dublin is one of those rare cases where the reality not only lives up to the hype, but actually succeeds it. And I can sufficiently say that I've had some of my best nights out ever in the capital of the Emerald Isle. Wherever you go, people are up beat, lively, friendly, and above all, fun. I debated internally back and forth whether this would be number one, but unfortunate obnoxious tourist presence and fairly high prices dropped it a notch below Tbilisi. Nonetheless, it's still awesome and especially if you go to a local place, you're in for a great night (just do a little pre-drinking beforehand to save a bit of money).
What makes Budapest's nightlife great is it's uniqueness and affordability. Out of everywhere I've been, I still haven't come across anything quite like the Ruin Pubs which and don't think I ever will. The mixture of abandon factories, art projects with discarded furniture, cheap drinks and raging nights packed with belong to this city and this city alone. The only downside it that it is becoming increasingly flooded with backpackers and overprivledged 18-year olds on gap years, and locals can be often hard to come by. For that reason, it doesn't get the top spot, but still, it remains pretty awesome.
Ok, so I may be a little biased for my ancestral homeland, but Krakow's nightlife blew away all of my expectations. It was so open and relaxed, in the best way possible. For example, many bars stay open 24 hours, everyone seemed to be dancing and enjoying themselves without being intense and in-your-face, and when my friend Blake ordered six run and cokes at once, the bartender handed them over without hesitation. Also, as opposed to Budapest and many other cities, most of the people (even those on the pub crawl) happened to be locals. I guess it didn't have the unique flair of some other places, but Krakow still holds its own very well.