Almost all of my 9 year old brother and his friends use Starter / Unfezant / Cobalion / Terrakion / Virizion literally just because it was a "cool legendary" and "easy to catch."
I hope that the legendary capture "puzzles" are more like the Regis, that was fun and hard. :3 I actually felt like a caught a legendary creature instead of a interactable Pokemon that was basically just presented to me!
I also hope that they don't pull a "buy this extra game called Dream Radar to get new formes!" because it's a hassle to get $3 on the 3DS for it. (took a while for it to work on my brother's)
I also really liked how in BW2, you weren't given the option of capturing the mascot as part of the main storyline. Since I knew that it was catchable somewhere, I actually had to go and figure out how to get it, which was nice. :3
I kind of like there to be a story behind why you're searching for it, or some sort of puzzle to solve to get them. It gives it more point. At the moment in Black 2 I just seem to be aimlessly running around to where I know legendary Pokémon are, starting a battle with them, and catching them, which has limited fun.
As for the difficulty of capture, I'm fine with the way it is. Sometimes I find it easy to catch them, but other times I find it challenging, and I think that's the right way for it to be.
My favourite way to encounter legendaries is while exploring optional areas I was wanting to explore anyways. I like the mystery of exploring a cave and wondering if there's just going to be a rare item at the end, or a legendary. I also wish that the legendaries weren't plot points anymore. In red and blue all the birds and Mewtwo were pretty much a secret until you found them. Now the legendaries are always on the box or in the opening credits sequence. It kinda makes finding them less special when you know they're coming. If there's one thing Black 2 got right with legendaries, it was that there were no wandering legendaries. Those are the worst since it doesn't feel like you're having a grand battle with a mythical beast when they just run away all the time.