IKAG sounds fun and refreshing compared to most of what's followed since.
It's super crass and tacky. Teenage Dream singles are catchy and fun but only for the first couple listens. I'd prefer them over ANY non-single from OOTB, or any of the singles bar WUIV.
PRISM is so much better than all of the crap she has done in the past. Katy her artistic growth is pretty amazing. To go from something as horrid as IKAG/HNC to one of the best pop songs of all time TIHWD.