Here are my two cents - for the purposes of full disclosure, I support the Hamburg bid. Nonetheless, I'd like to think that I can evaluate the merits of each potential bid quite objectively.
ROME: I know there's always talk of Rome being a viable Olympic City. It's not, despite the Coliseum, St Peter's, the beautiful piazzas and its rich history. Italy's citizens have much bigger worries to fight with right now, including a weak and inflexible economy which could tip into disaster at any stage. Italy's debt is catastrophically high (whilst having an economy eight times the size of Greece's), there are doubts about its ability to retain the Euro (and conversely, debates about the return of the lira), its economy projected to contract (instead of growing), its long-term credit rating cut and unemployment at 13% (youth unemployment being 43%).
After the last Olympic Games in a Mediterranean country (Greece), in which it is now established consensus that Athens 2004 accelerated the country's debt burden and economic decline (and subsequent de facto fiscal administration from Brussels), would the IOC once again wish to risk a financially doubtful and irresponsible bid? The Rome City Council had to be bailed out by the central government. Talking of which, given Italy's volatile climate, it's far from assured that Prime Minister Renzi will not crash and burn politically - and be forced to abandon the Rome bid by the resurgent Five-Star movement of comedian Beppe Grillo. Expect more discussions about how the IOC is detached from reality, letting hard-working Italians pick up the tab for the Rome elite's little party and populists to get increasingly stronger. And an image loss in Europe, where bids are already declining.
In an opinion poll, 60% of Italians stated that the country cannot pull off the Olympic Games.
Finally, the IOC has tended to favour politically economically resurgent countries for the Summer Olympics:
Seoul 1988: politically stable (military dictatorship) and great economic performance
Barcelona 1992: successful transition to democracy with a stable government and fresh entry into the European Community and influx of cash
Atlanta 1996: The Bush recession hadn't begun yet, America at height of its international recognition after the end of the Cold War, a big TV market
Sydney 2000: Prime Minister Keating had just been re-elected for an unprecedented fourth term for the ALP and was an avowed supporter of the Sydney bid. Plus, major concerns about China's human rights record (Tienamen Square etc), with the Australian economy emerging from recession
Athens 2004: The notable exception. Why? Because Greece underreported its debt figures; Plus, the country was "owed" the Olympic Games after the Centennial Games ended up in Atlanta's camp
Beijing 2008: Politically very stable (nothing more stable than an autocratic dictatorship), on the ascent (Hong Kong and Macau returned, world forgetting about Tienamen) and economically rising
London 2012: Despite the Iraq War, Blair's name still had a "pull" with the IOC, the UK economy was doing rather well, a strong pound sterling, plus better economic performance than EU; combine that with Chirac's comments and Paris' technically perfect, but soulless management of its bid, and you got London 2012
Rio 2016: Brazil one of the BRICS countries; young population; economy and social inequality were less of an issue than they are today;
Tokyo 2020: Whatever you might say about the whole Fukushima thing, within a weak field (a disastrously positioned Istanbul bid and a financially untenable Madrid one), Tokyo still had the strongest cards to play
No financial stability, no political stability and no image gain - there are more reliable candidates, in Europe and elsewhere. Bach would have to be seriously desperate to seriously (beyond politeness for the cameras) entertain the idea of Rome 2024. Considering the IOC's emphasis on sustainability (re: Agenda 2020), Rome should be completely, utterly dead-on-arrival.
PARIS: Won't bid, according to Mayor Hidalgo. I take her at her word, especially as President Hollande's popularity was in the toilet prior to Charlie Hebdo (granted, there has been an upswing to 40% after the attacks - but the numbers are likely to drop off after the period of national mourning is over) and his support of the bid looks like a desperate attempt to distract from disastrously high unemployment rate, a major economic crisis and the country's growing debt. France has no narrative of aspiration or growth to offer to the IOC.
DOHA: Two words: Qatar 2022. Three more words: FIFA World Cup. One more word. Corruption. The atrocious climate aside, the horrific reputation of Qatar in regard to treatment of its guest workers, its location on the perennially unstable Arabian peninsula and issues with things like beverages, dietary requirements, dress codes and the like (can you imagine the Qataris standing for beach volleyball played in the type of skimpy attire regularly featured in the Olympics?) make Qatar a no-go. Forget it. Plus, the Middle East isn't exactly a growth market right now.
ISTANBUL: Syria's proximity kills any chances of the IOC contemplating another bid. Oh, and Prime Minister Erdogan - apart from being a religious zealot, a historical revisionist and authoritarian who refers to protestors as "terrorists", the kind of country he is turning Turkey is about to hand over its greatest unique selling point: being a bridge between West and East.
GERMANY: Strong and best-performing economy in the Eurozone; scheduled to balance its budget this year (ahead of schedule), inflation relatively low; unemployment at a low 5%; strong Olympic tradition (to be fair, just like France and Italy); Minus points: Mass media tends to focus on risks of projects; white elephants of Athens and Beijing have been registered; plus, TV channels adopted a rather moralizing (and frankly, annoying) social commentary on Sochi and Beijing; every small decision (like Games Lanes) etc would be dissected into oblivion; Count on populist movements from right and left to condemn any Olympics bid as being part of a major plot by corporatists to consolidate their evil power (I know, I'm exaggerating - but you get the drift)
BERLIN: The population there doesn't really back the bid (47% are already against it, and that's prior to any discussion). The city is structurally left-wing in its politics, which makes a bid even less likely (that's a fact of life; Germany's Greens are naturally opposed to anything that smells of "international corporations" or "big business" - as is the country's Left Party); no real industry or commerce of note (most corporate headquarters are in Munich, Frankfurt or Hamburg); massive public debt, huge welfare rolls, structurally high unemployment; scepticism towards new construction projects after the city government bungled the construction of the international airport; plus guaranteed resentment against the capital from the rest of the country; given that the mayor has already announced that a public referendum will take place, Berlin (despite its technical strengths) is dead on arrival. The last time Berlin ran a bid, the federal government only lukewarmly supported it. I wrote about the Berlin v Hamburg issue almost three years ago - and I believe it's still valid.
HAMBURG: Strong middle class, prosperous city (with one of the highest per capita GDPs in Germany) where Social Democrats might as well be conservatives. Broad support exceeding 70%; drawback: those guys bungled the construction of their Philharmonic; here too, a referendum might derail the bid - but based on opinion poll has a better chance at winning. Intriguing idea of Games by the sea.
BOSTON: I firmly believe that it's not the best foot America could have put forward...
One more strong point about Germany: Its infrastructure (roads, railways, airports) is first-class...Rome's - not so much, if you believe Romans