Two Worlds... The basic engine did everything right. Huge free-roaming world, scattered wildlife, some hunting, great cities, abandoned places etc. Exploration was fun and the game suceeded on that unlike Oblivion.
My first great issue was balance. I quickly earned the 15 skillpoints neded to master fire magic and I could actually have beaten the game like that. I had like 99.75% combat efficiency at the end of the game, relying almost exclusively on 3 spells from the firemagic school. (All my deaths happened in the first hours of the game while learning the controls). Close to the end I exchanged my fire damage booster to an air damage booster with the same effect but doing so gave me a microscopic improvement which I doubt had any greater effect since i one-shot killed most opponents anyway. The balance between the monsters simply wasn't there. Either monsters was a one-shot kill, or they had lots of HP and could kill you in a blow, but since they moved so slow they were never any danger. I sometimes ran around in circles, gathering 20-30 monsters after me, then I picked them off by using areaspells, still not taking any damage. Due to alchemy I had a ridicilous amount of hitpoints as a mage. Even in the end boss battles I took zero damage. In fact, I just messed around with some spells that I hadn't used before just to try them out, so I nailed them to the ground with ivys and poisoned them to death.
All in all it seems they wasted their energy on warriors, while they forgot to flesh out the mages. I barely had any use at all for equipment and I had my staff on my back throughout the entire game. I used a robe because it looked good. If I just wanted more defense I could have used the strongest heavy plate in the game without penalty.
The second problem was the quests and the annoying dialogue that tried to sound like shakespeare. Sure, the quests had some variation and some surprises but they failed in sounding important. Just like the main quest. Writing good dialogue and making a story feel interesting and important takes skill. It's actually possible to take the most over-used elements and still make a grasping story out of it.
I was also annoyed at my lack of options. Sure, there were more than average among the "modern" RPG's, but sometimes I still felt that my character played me instead of the other way around.
I think they are going to need someone who understand balance and can design roleplaying mechanics. They also need a good storyteller, who knows how to make a story interesting.