The second game really is an exponential leap in quality. It's much less repetitive, and Ezio is a much more likable character than Altair.
As for the stealth thing...meh. The social stealth aspect in AC2 and Brotherhood works great, but it does sort of go in a direction where it's more about an almost open conflict between the Assassins and the Templars. The real life Assassins killed their targets as publicly as possible to send the message that no one was safe, etc. They just didn't have magical parkour skills and were usually killed on the spot. So I've never had an issue with the idea of killing your targets so openly then having to run away.
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Gamertag-Murphiroth
Pokemon Black-1978-9490-1161