Just posted in that similar thread... And here's that post. Run n Gun is the only freemium in that list as TheEndApp is a one time iap to unlock all modes and upgradeables. It also isnt as grindy as the freemium runners as this game has tons of it.
Originally Posted by Exact-Psience
Too broad to make a list of. Even casual games have tons of upgradeables now to give them replay value. Temple Run and its clones all have good upgrade systems... Cookie cutter, but they all work fine.
Then there are the well accepted RPGs, with so many subgenres each with their own character progression system. From the menu bassed, turn based combat of kemco's gems, to Crescent Moon's innovative games, to SE's Chaos Rings titles, to the well-proven Final Fantasy titles, the upgrade systems are all too present, and pretty much a big part in playing the games.
Tons more to mention as upgrade systems are everywhere, but here are some games that get my highest recommendations.
Chaos Rings 2
Run 'n' Gun
Heroes & Castles
Mass Effect Infiltrator