Depends in which forum you ask. Here the answer will be the original Final Fantasy Tactics.

To be honest I've never played FFTA, but I can vouch for the playability and replay value of Tactics. I got it when it first came out and I'm still playing it!

The durability of Tactics lies in several areas:

Job systems allows you to customize character classes. And instantantly change classes with no hassle. No other FF is so flexible.

Interesting characters. And enough of them that you can pick your favorite, but no so many that it's overwhelming.

Involving plot. I can't overstate that.

Great music.

Monsters that can be recruited, bred and poached.

Lot of hidden items and subquests.


Other games may be flashy and exciting, but this is the one I always go back to.