Important Metro/Subway Card

Hello guys, how are you doing?
I'll be going to Japan very very soon and I'll be using the subway in several cities in Japan as my only way of transportation.
I want to know which is the main (and the best and more used) subway card in Japan. One that can be used in several cities, for a good price..
Can someone help me??
Thanks :)

Which cities would you visit? Actually is you use "only" metro/subway, you might not be able to get too all places in, for example, Tokyo. You will probably want to use both trains and metro/subways.

Most city transport cards in Japan are only prepaid cards, meaning not saver cards but more for convenience (you simply don't have to buy individual tickets every time you take a train or subway), such as SUICA or PASMO in Tokyo.

There are other saver type of train passes for JR nationwide use, or regional use. So we'll need to know your general itinerary to be able to help you better :)

In general the one day passes are difficult to make pay off. Instead, it would be more convenient to use a prepaid IC card. It doesn't get you any savings, but streamlines the process for taking the trains in most cities.

http://www.japan-guide.com/e/e2359_003.html

Suica is marginally best.
There isn't much difference but I noticed when I was in Kyoto that my friend's passmo didn't work but my suica did.

takeda's ghost
: when I was in Kyoto that my friend's Pasmo didn't work but my Suica did.

Presumably it was before 23 March 2013 and on a JR-West line. Since that day Suica Cards and PASMO Cards have been acceptable on the same lines.
There are still some non-JR lines which accept only IC cards originated in the same area, but there is no line which accepts only one of Suica and PASMO.

One that can be used in several cities, for a good price..

I suppose a subway pass in Japan is designed for one designated transportation network.
I have never heard of a subway pass which can be used on plural networks.
e.g.
A Tokyo Subway Ticket is designed for Tokyo Subway Network (of Tokyo Metro and Toei subway lines), and it cannot be used on another subway network.
An Enjoy Eco Card can be used on Osaka Municipal subway and bus lines, and it cannot be used instead of a Kyoto Sightseeing One-day Pass Card or of a Kyoto City Bus - Kyoto Bus One-day Bus Pass.

I want to know which is the main (and the best and more used) subway card in Japan

I assume subway passes are not very popular in Japan, at least not often used by passengers other than travelers.
Especially on Tokyo Subway Network and on Osaka Subway Network, fares are set already at low prices, and it is not easy to make a subway pass pay off unless a passenger travels here and there by subway within the term of the validity.

I'll be going to Osaka, Kyoto and Tokyo.
Does de SUICA works for this cities??

You can get issued
an ICOCA Card at a JR Ticket Office in a major JR -West station in Kansai Region
or a Suica Card at a JR Ticket Office in a major JR -East station in or around Tokyo
or a PASMO Card in a major non-JR station in or around Tokyo.
A deposit of 500 yen is required per card.

Any of these IC transportation cards can be used on most railroad (including subway) lines in Osaka City, in Kyoto City and in Tokyo Metropolis.
It is recommended that you do not hold plural IC transportation cards together.

Note
: Kyoto City Bus lines / Kyoto Bus lines are not accepting IC transportation cards. For major tourist spots along these bus lines, a Kyoto City Bus - Kyoto Bus One-day Pass (available for 500 yen per adult) can be useful.
: Eizan Electric Railway lines (in Kyoto City) are not accepting IC transportation cards.
: Many bus lines in Kansai Region are not yet ready for Suica / PASMO.
: Some bus lines in and around Tokyo are not yet ready for ICOCA.

Please also check "Basic Use" in this article.
- japan-guide.com: IC Cards
http://www.japan-guide.com/e/e2359_003.html

E-money stored on your ICOCA / Suica / PASMO Card can be valid for 10 years after you use the card last.
You can allot the e-money also for payment in some shops (including those of major convenience store chains).

You can return an ICOCA Card / a Suica Card for a refund only to the company which issued it; you cannot get a refund of the e-money in a station of another JR regional company.
You can return a PASMO Card for a refund only to a transportation operator joining PASMO; you cannot get a refund of the e-money in a JR-East station.

Thank you very very much!!
:D