LOL, Headhunter. I had it on Dreamcast, it sucked.
Is it still worthwhile to have a Japanese PS2? I haven't kept up with import titles since my Japanese PS2 died. The last import title I bought was one of those Gran Turismo mini games.
Beyond some the mecha and fighting games, I can't think of too much that hasn't made it Stateside at this point.
Some stuff I have that I'd recommend is-
Fighters:
-KOF 2002 Unlimited Match (SNK)
-KOF Maximum Impact Regulation A (SNK)
-Garou Mark Of The Wolves (SNK)
-Fu'un Super Combo (Savage Reign and Kizuna Encounter) (SNK)
-Sunsoft Collection (Galaxy Fight and Waku Waku 7) (SNK)
-Twinkle Star Sprites (Remake of the original) (SNK/ADK)
-ADK Spirits (Ninja Combat, Ninja Commando, Ninja Master's, Gan Gan/ADK, and Twinkle Star Sprites-- it's worth it just for Ninja Master's) (SNK/ADK)
-Shin Gouketsuji Ichizoku: Bonnou Kaihou (AKA Power Instinct Matrimelee, updated a bit from the Neo version) (Excite/Atlus)
-Vampire Darkstalkers Chronicle (Has all of the Darkstalkers games) (Capcom)
-Fate: Unlimited Codes (Capcom and like four other companies, lol)
-Basara X (Capcom/Arc System Works)
-History's Strongest Disciple Kenichi (Capcom/8ing)
-The Rumblefish (Sega/Sammy/Dimps)
-Hokuto No Ken (Sega/Sammy/Arc System Works)
-Melty Blood Act Cadenza (Ecole/Type Moon)
-Suggoi Arcana Heart 2 (Examu) (Releases 4/9)
Other:
-Sengoku Basara 2 (Capcom)
-Sengoku Basara 2 Heroes (Capcom) (I highly recommend both of these; kick-ass beat-em-up series from Capcom, spanks Koei games all over the place)
-Oz (Konami) (Interesting beat-em-up action game)
-Gunstar Heroes Treasure Box (GSH, Dynamite Headdy, and Alien Soldier) (Sega)