Google's Roboto is a Helvetica rip-off

I know close to nothing about typography, but is it really so odd for letters to look similar in different fonts? They're the same letters... it seems like they can only differ by so much.

Personally I think the differences, even if they're subtle, make Roboto feel different (I seem to like it more than Helvetica, just from my reactions to it from staring at that picture)