>>55186321DP and BW both do it really well, for different reasons.
In DP the wild mons are only a level or two below the trainers in their area, and the trainer levels remain fairly low, raising slowly (especially in the midgame). This makes it easy to add new mons to your team since you can use them right out of the gate. On the flip side though, the Boss battles (Gym leaders, Evil team leaders, and especially the E4/Champion) are often a considerable jump up in levels, which encourages the player to go in under-leveled, which I like as it gives them an air of challenge to contrast the easy-going feel of the rest of the game. There's also a few points in the game (especially towards the end game) where there are considerable level jumps, which allows the level curve to catch you by surprise at times with sudden leaps in difficulty. Overall, DP handles levels pretty uniquely, but I like what they accomplish, it allows for the level curve to feel easier and more forgiving at certain times, and steeper and more difficult at other times, which I feel is handled well throughout.
BW, on the other hand, take a different approach. The levels of the trainers raise incredibly consistently, and generally there's not a significant gap between the levels of trainers and the levels of gym leaders. The wild mons are also fairly close in level to the trainers, and with dark grass you can even find wild mons that are above the levels of trainers and closer to the levels of the next gym leader. All this, combined with the exp-scaling introduced in this gen, gives the level curve a very closely controlled feel. You'll pretty much always be just a few levels higher than the trainers and around the same level as the gym leaders, once you battle them, and adding new mons to your team is usually pretty easy. Overall I consider it to be a very solid way to handle the level curve, it's certainly accessible, if a bit boring.
Fpwp 
