I love a good turn-based game, but very often they're not that good. Either they're too easy and present no real challenge (as much as I love FFVI it falls into this category...), or the 'challenge' consists entirely of grinding because the decisions you can make just aren't as important as your stats. It's important to present the player with multiple viable options and force him/her to make tough decisions.
Honestly, one of my favorite modern turn-based systems is what Falcom uses in the Kiseki series. I love the fact that all your abilities are actually useful and as the game goes on you get more viable options rather than just replacing weak attacks with stronger versions, etc. I love the importance of positioning (without going full SRPG), the use of tank skills, the options for turn manipulating, etc. It's a really deep system. Battles can be challenging without feeling cheap. Make more games like that.