What is the best Rail Pass?

It is a 6 days trip.
Day 1 Narita
Day 2 Disneyland
Day 3 Shirakawago
Day 4 Osaka
Day 5 Universal Studios
Day 6 Kansai Airport
Is it JR Pass or Hokuriku Arch Pass or Takayama-Hokuriku Tourist Pass? I will only save 2,000 yen if I buy the Hokuriku Arch Pass because the bus to Shirakawago is not included. Kindly help me decide. Thank you very much.

Use Hyperdia (hyperdia.com/en) to look up the prices of trips, and put them into a spreadsheet. Then add up the costs and compare to the rail passes to make your decision.

Don't try to cover every trip with a pass; you may find that only trying to cover some trips works out to be more cost-effective. You should also consider smaller passes for trips to and from airports (e.g. there is a discount ticket offered for the Nankai service to KIX from Osaka - Google it).

Note that Tokyo > Shirakawago is a very long trip, and in fact your trip in general is very rushed. You will spend a lot of time in transit and not much actually seeing Japan. I would go straight from Tokyo to Osaka and skip Shirakawago as you simply won't have time to actually visit it properly. I would also choose either Disney or USJ, not both - these theme parks are similar to their counterparts outside Japan, and don't give you an experience you can find in Japan alone. When in Japan, actually see it! In six days, two days at theme parks is overkill.

There is no guarantee of saving money on a rail pass. It depends how far you travel and for how long. I'd say you can get a bit of savings with the Hokuriku Arch Pass if you include going to/from the airports.
But it wouldn't cover the buses to Shirakawago, as you seem to be aware. Also to get up there from Tokyo will take you close to 4 hours. Fortunately it does not take long to see - just a few hours are enough.
https://goo.gl/WKGLMN
Be sure not to miss the village overlook.

What is the best......It depends on person. As a student,my source of income is Limited. More than 40%of my part time job income go for house rent and mobile bill,so in my case Japan bus pass 7 day=15000
Yen is the best transport pass to go Tokyo,Osaka,Fukuoka etc.

Thank you for the replies. We are going to stay overnight in Shirakawago and planning to visit a ski resort near the village. Im also considering to buy the Takayama-Hokuriku Area Tourist Pass and just buy the ordinary train tickets in tokyo since we will only visit Tokyo Disneyland. We will only stay in tokyo for 2 days.

If you want to save some money on travel, there is an alternative route to Shirakawa-go that is a lot less than the Hokuriku Arch Pass or the expense of the shinkansen to Kanazawa, but it takes longer. Tokyo to Matsumoto by train and then bus to Takayama and onward is a scenic option. (You could take the bus Tokyo to Takayama and then Shirakawa-go, that is an option too.)
As you are basically doing a one-way trip Tokyo to Osaka without the return it is difficult to get good value out of the two passes you mention.