I agree that KB:L is much more polished than SR2.
But SR2 did have significantly more "pick up and play" quality, which I felt was actually similar in a lot of ways to the original King's Bounty that I played in DOS and on Sega Genesis. KB:L seems to more focused on definite progress, kind of like an adventure game or RPG; it's not as much of a "sandbox" as the other two games.
And that's fine, I'm not complaining.
But it does mean that those games have, by design, a bit more replay value than KB:L, so maybe there are ways to compensate for that. Not in this version, of course, which is both finished and awesome, but maybe in a sequel or expansion.
For one, more random content, like in SR2. Strange stuff that you'll just stumble on or that could stumble upon you. The continents, dungeons, caves, etc., in KB:L are not randomly generated and I think the game is better off as a result - but the NPC's or the quests that they give could be randomized or "rotated," so that you would be faced with different characters and tasks each time you play the game. KB:L already does this with items and recruits.
Anyway, I'm not saying that the game has a "huge flaw," I'm just talking about a means of modest improvement. In any case KB:L is one of the best games I've played in a long while. It has more choices-and-consequences than most "real" RPG's, and I like that it doesn't "hold your hand" through quests or treat you like an idiot with tutorials and cutscenes as many console games/ports do.