Sorry, but short of Seiken Densetsu 3 you're not going to find anything even approaching that magical sweet spot on any system (and the game was never released outside of Japan, so you'll have to scrounge up a ROM version someplace). It's been over fifteen years: I think we need to give up hope.

Virtual Console may be your best hope, but the Enix games mentioned don't seem like they're coming anytime soon.  

what about.....Allundra on PS1? Its good, but more in the vein of Zelda..

Alien Syndrome is about the closest you're going to get (basically a sci-fi version of Baldur's Gate: Dark Alliance and other, Snowblind Studios-like, productions). It's about the ugliest game on Wii (a straight port, literally, from the PSP version) but, despite this, it's pretty entertaining.

Secret of Mana is a very unique game. Its kinda of a cross between Zelda, Final Fantasy, and Gauntlet. There really isn't anything like it on any system.

I suggest you play through again and this time bring a friend along.

also, get and emulator and download a translated copy of Seiken Densetsu 3.  Not quite as good as SoM but it is the closest your going to get.  

There isn't much like it on the Wii. The only thing close to that kind of multiplayer ARPG experience is the new Tales of Symphonia which isn't out yet. Might as well do what everyone else says and clean out all the SNES ARPGs.

Of course, you can also wait until SE announces Mana Wii at E3 and hope it's like the older games.

 Are you kidding me? Almost every rpg is going actiion. I would say the days of the turn based rpg are gone. 

He said glorious.

Turn based isn't going anywhere. Developers just aren't rehashing it as much.

arent their mana games on the DS?

 Yeah, but they are srpgs. I think they are called heroes of mana, and children of mana. 

@ Claude True, but there has to be at least a few good ones. 

Don't look in a desert if you want water.