Paris-Brussels-Frankfurt in 14 days
 

Friends,
My wife and I are planning a trip to Europe (as a first anniversary present to ourselves.) We have 14 days and will arrive and fly out of Paris CDG. We would like to experience Paris, Brussels, (with day trips to Bruges and Amsterdam) and Frankfurt.We'd appreciate any insights and tips regarding rail transportation between these cities.

We're looking for recommendations for hotels in the Quartier Latin or Montemartre areas of Paris. We'd love to experience local neighborhoods by foot, bicicle or moto. We're budgeting approx. $200 US per day.

Thanks in advance for your advice.

When are you doing this?
What are you looking to "experience" especially in Brussels and Frankfurt? The latter is a modern business city not much distinct in appearance from other modern cities you see all around the world.
I presume you have already bought your round-trip ticket to CDG, so open-jaw flights is no longer an option to eliminate unproductive and time consuming trip back to the starting point.
You are already concerned about where to stay and how to connect destinations. It seems it is far more effective at this point to determine where to go first, then check the realities by the transportation constraints and the accommodation availabilities. For rail, you don't have to wait for someone else to tell you. You can look at options at www.bahn.com. If you trip is into next year, just use the same day of the week next week. The train schedules don't change to much. You can get a feel of the frequencies and the trip time. For accommodations, even if you don't book through them, you can grasp the availability and the price range by hovering over map at www.booking.com. If the price seem too high, look at a week before and after. If your target week is high, it is possible that there is something going on in the city skyrocketing the overnight stay prices. Business cities, several mentioned in your current list, are susceptible to convention driven pricing. Frankfurt is one of them.

Do you have some personal reasons for Frankfurt? Brussels?
Dates for this trip? Do your 14 days include travel days to and from Europe?
Do you already have tickets? If not, look at multi-destination (not two one-way) flying into one city and home from another, saves time and money backtracking.

Amsterdam is too far to be a good day trip from Brussels. Bruges is pretty and worth a day and one night. Nearby Ghent is lively with lots of cafes, music, etc. along the river. Young vibe.

With 14 days (minus 2 for travel), you could have 4 days Paris, train to Amsterdam for 3 or 4 days (lots of interesting small towns and sights to see), drop back down to Bruges, Ghent and depart from Brussels.

You could do Paris, then train over to Germany. Just choose more carefully what you want to see in Germany. It would not be Frankfurt for most people.

Imagining you have a reason for your destinations, best way to Bruxelles is by fast train - Thalys Bol 3 months in advance for best fares.
From Bruxelles you have a fast trai. To Frankfurt called ICE.
To gent or Brugge take normal trains.
If going to Amsterdam take the thalys again.

I guess you must have some personal reasons for Brussels and Frankfurt, because of all the many destinations in Europe they sure wouldn't be on my list. Well, Brussels might for a night or two, but Frankfurt? You couldn't drag me there except for a business meeting. Take the Thalys to Amsterdam and get your tickets plenty of time, like 3 months, in advance. It's not really a daytrip.

Is the US$200 a day for everything - accommodations, travel, sightseeing, food? Is it for both of you? If so, that could be a stretch.

Do you have RT tickets to Paris? If so, that's a shame because you're going to have to spend time and $$$ to backtrack. I'd pass on Germany for that reason alone, never mind that Frankfurt is a no-go destination.

There are hundreds of reccomendations on this site for hotels in the Latin Quarter, though I never stay there and don't ever want to. It's a good spot for newbies to Paris, though. But I cannot imagine using a moto there or anywhere else you're headed. Use the métro and buses and your feet and you're good to go.

With the others I advise the combination of Paris, Gent and Amsterdam. All close to each other (the longest distance Paris-Amsterdam is just over 3 hrs with the Thalys), and Gent is the perfect base for Brugge and Brussel (each some 30 mins away).