Few games manages to make every battle enjoyable. But if I were to mention a single game that I think manages to do this, I'd probably say Endless Frontier. Even when it's that same enemy formation you've seen 30 times already, it's just so FUN to keep smashing them around with crazy combos and finish them off with extreme overdrives that never gets old and basically makes every FF limit break ever look boring and dull when compared.
I actually played the second game (SRWOG Saga: Endless Frontier EXCEED), even though it doesn't have an english translation, because all you need in order to enjoy that game more than your average DS game is the battle system. Especially once you get the secondary overdrives that were introduced in EXCEED. Especially Suzuka Hime's. <3
...I can seriously pick that game up just to go fight some random enemies and enjoy the hell out of that awesome battle system.