You are at the right place. Use the search button and you will find a plethora of opinions on the best joystick/buttons.
The most popular buttons are the Happ horizontal buttons. A good, all-around joystick would be the Happ Super. These are also about the least expensive.
On the high end, but definitely worth every penny would be a 49-way joystick with the GroovyGameGear GP-Wiz 49 encoder and the GroovyGameGear translucent buttons with RGB LED boards controlled by the LED-Wiz light controller.
Before you purchase anything, look at other projects and read what joysticks/buttons they chose and why. I have tried just about all of them.
Two vendors to look at are:
http://www.groovygamegear.comhttp://www.ultimarc.comFor Happ parts I like a vendor named Terry Bell in Texas:
http://www.tornadoterrys.com/surplus.htmThere are also two very reputable parts resellers here on this forum named Divemaster127 and Ponyboy. You can find their threads with products and pricing in the Buy/Sell/Trade board here on this forum.
Good luck with your project. I highly encourage you to create a PROJECT ANNOUNCEMENT thread in Project Announcements to keep us updated and to get help as you go.
One thing to consider is that some games used 4-way joysticks (Pacman, DonkeyKong) and don't work well with