Nah, shows like Lost in Space were the best thing for Star Trek. Think about it; if high quality, adult, intelligent, message-carrying sci-fi shows were the norm back then, Star Trek wouldn't have even been necessary. Star Trek needed Lost in Space to compare favorably with and to prove the point that "it doesn't have to be like this."
Ahhhhh... I can almost hear the discussion in the production meetings for Perry Mason... "Thank goodness for Gilligan's Island
or no one would watch our show!"
Seriously though... you could swap Gilligan--character and actor--for Dr. Smith and it wouldn't amount to a ant hill's difference in the two shows. I don't think I can make the same claim if we swapped Shatner/Kirk's character with the elder Robinson.
Wait... but now that I think of it, the character of Will Robinson does remind me (annoy me, actually) the same as the character of Wesley Crusher.
I have to stop this line of thought as it's giving me a headache or maybe brain damage.