Raiden 2: yes, go for it. its one of my favorite shooters.
very challenging, and it has the old-school bullet patterns (fast, aimed directly at you) and loops after clearing the last stage. gameplay is straightforward: shoot everything, dodge, and manage your weapon level.
the first Raiden is a classic, and is not all drastically different from part 2. it basically lacks the homing laser weapon that's become standard in the series.
the "Fighters" games I have not spent much time with, but Jet seems pretty cool. the bullet patterns are a bit more modern and the game is full of secrets and hidden scoring tricks to figure out.
every Raiden board (with possible exception of part 3) is standard JAMMA. the "Fighters" games are all on Seibu's SPI hardware, which uses a ROM cartridge and motherboard. single PCB versions of the Fighters games exist too, but I believe that they use lower quality sound chips.
there are two different versions of the Raiden 2 PCB:
- original 1993 release, with high difficulty and a battery for saving scores.
- smaller 1996 re-release, with adjusted difficulty level and no battery.
sound is apparently crappy on this version too.
I recommend sticking with the bigger '93 version board.
for price, I think around $60-75 US for an original US or JP Raiden 2 PCB without any extras is typical.