Train Confusion

Check prices of advance purchase nonrefundable tickets. Two issues I see with rail passes.
1. Thalys train (Paris to Amsterdam) charges very high mandatory reservation fees. As much as advance tickets, which come with automatic reservations.
2. TGV train (Geneva to Paris) besides charging a reservation fee on top of the pass, it limits the total number of pass holders on any given train. So you may not get the train you want even if it has plenty of empty seats.

You can get prices at:
Paris to Amsterdam https://www.thalys.com/de/en/
Amsterdam to Frankfurt to Interlaken http://reiseauskunft.bahn.de/bin/query.exe/en
Interlaken to Geneva http://www.sbb.ch/en/home.html
Geneva to Paris http://www.sncf.com/en/passengers

You can buy on-line and print tickets at home. Interlaken to Geneva can be bought at the station.

Advance buying of your tickets (some three months before) at the relevant railway company (such as Deutsche Bahn for trains going to or from Germany) is in most cases the most economical way. Read www.seat61.com/ for reliable practical information.

Pardon my unsolicited advice, but: Don't end in Paris. Fly home from Geneva. It will be a better trip.

I am not sure I would agree about departing from Paris. I find Paris a difficult airport to transfer because of size and scattered terminals but departures are fairly easy.

I found CDG somewhat chaotic and disorganized. So if I could I would avoid it.

Decide where you want to go first. If the itinerary is not yet very fully planned, then you can't really compare your train ticket or rail pass needs.

Do look at "multi-city" flights instead of roundtrip to Paris to save an expensive train ride and the half-day that it takes. I would probably fly into Amsterdam and out from Paris, but other combos also work.

Why these destinations? We would not particularly recommend the cities of Frankfurt, Interlaken, or Geneva as sightseeing destinations for a short or first-time trip to Europe. Instead, stay in smaller towns in those regions, where the touristic action is. If you already have some in mind, then go ahead and tell us the destinations. There's no need to use "short hand" and it can result in the wrong advice. If you can't guess the towns I have in mind, get a start to see Rick's favorites under the Explore Europe tab.

If you do buy a few longer-distance train tickets with advance discount, then you probably still could use a Swiss Travel Pass. It gives you a lot of coverage for the unmentioned transportation and sightseeing you might do within Switzerland. At the same link, see some differences in Swiss coverage with a Eurail-brand pass, such as the 4-country Select pass.

Fly in to Amsterdam
Go to Thalys for train ticket from Amsterdam to Paris
Go to sbb Swiss Railways for trains:
Paris > Geneva > Interlaken > Frankfurt
Fly home from Frankfurt

I was not critiquing deGaulle, I was trying to save the OP a day of needless travel.

Amsterdam in, Frankfurt out works too, that is not a bad itinerary at all.

Thank you for the help, I am assuming that a rail pass does not work in the city's for traveling, the metro and such. Is it best to purchase a 2 or 3 day pass in Paris and Amsterdam. Or is walking a better option.

Rail passes don't work for urban transit. In Paris, you can buy a carnet, which is a 10-pack of tickets that can be used on the Metro, city buses, and RER within the Paris city limits for 14.50 EUR. In Amsterdam, a 24-hour pass is 7.50 EUR, 48-hour is 12.50 EUR, 72 hour is 17 EUR.

It will be more time efficient and economical to fly in one city and our another, "open jaw." Yes the airfare may be more, but you have to pay to return to your entry city.

Crunching the numbers is always a good idea, but generally speaking rail passes are rarely a savings compared to advance purchase tickets.

I suggest getting Rick Steves Europe and some individual country Insight Guides from the library. Steves will help you with logistics. Insight will help you armchair travel. Use them to pick where to go. Then get RS Guides for the places you decide to go to. Your trip is short and multi country. Rick Steves is perfect advice for that. Should you decide to stay longer in smaller towns on a later trip get a Lonely Planet or Rough Guide.