I agree with Blaze in your statement; she felt like a really great new character for the Sonic series. Will go into this in a lot of depth when I cover Rush, but I love her design, her general character arc and how she was a hybrid of Sonic (fast character) and Knuckles (guardian of Soul Emeralds).
She is a great character and they used her well in both Rush titles .
Shadow......is a lot more mixed to me :l. I love how he is the 'dark' Sonic and his personality in Adventure 2 and Heroes was strong. But Shadow the Edgehog came out and.......ugh X(. They ruined him .
06 ironically did a good job portraying Shadow as it was HIS game in many respects. He had the big foe, he did the most action, and he faced the most backstory.
I think he's great. Because like knuckles, he's a failure of a rival character. I'm not going to pretend His game was perfect by anymeans, but what it did was actually exspand his character. The only canon path in his game is the one to the true ending, which is the good path, so basically the only canonical missions in that game, is helping other sonic characters. Shadow despite going through inner turmoil put that asside to basically help people and help the planet he resides on, to the extent of basically killing of his real father and his whole family. Or most of it, eclipse exists in the comics.
He joined the organization that threaten to kill him, so he could watch them and help people. He's like this socially inept super good person.
But back to my orginal point, he's sort of a complete failure of a rival character. I mean yes hi m and sonic fight, but even in sonc adventure 2. Shadow doesn't give a cold shit about sonic, people often compare shadow to vegeta , but all in all besides being kind of grumpy, and hell a lot of times shadow isn't even grumpy, he's just soft spoken. Its even in a lot of his character descriptions, he's just .. reserved. He actually doesn't care about sonic, heck in sonic generations they have to time displace shadow from sonic adventure 2, to make that fight happen. He a lot of the time feels no need to prove himself.. because really strong. He's a character that is billed as a " rival" but all in all, He kind of doensn't care. He's the cody travers of sonic too, because well, dude fights with inhibtor rings on.
Heck when they tried to make shadow vegeta in sonic boom, folks got pissed and they have changed his character 3 times.
I'm rambling but my point is. I like shadow because he goes through this arc and becomes a generally way better person at the end of up. And extreme powerful, no vegeta gimmic, no nothing.