That's why I always go the paragon route. I would choose renegade Shepard if his responses weren't so idiotic and/or stupid. It's like in ME3 - the renegade choices almost always result in you choosing not to gain an ally for whatever arbitrary reason. That, or you're just a d!(k to everybody. I always hoped the ME team would make the Renegade more Bruce Willis/Die Hard bad a$$ than Schwarzenegger/Terminator 1 @$$hole.
Yeah, except for the one where you shoot Udina, that one was pretty awesome. I think you'll find this year's Renegade choices to be a little more not idiotic as previous editions.
I tried to do renegade for a little while on my second play through of ME3, but I just couldn't do it. Went back to paragon, but I paid close attention to the renegade choices just to see what I'd be missing out on. Seems like doing renegade would be a lot more difficult, considering that if a certain character/faction isn't integral to the story line, you have the choice of killing them or not using them as an asset. If you went full renegade, seems like you'd miss out on tons of helpful war assets.