IMO....Civic has been pretty much the same car since the early 90's. Sure, there has been technological improvements as well as slight changes in the body style but it is essentially the same car. The reason Honda can get away with very small changes every so often is that the Civic's core group of buyers really don't care that much about how fast it is, what it's skidpad numbers are, what it's top speed is...etc. Their two main concerns are fuel economy and reliability (price really isn't much of a factor anymore). If either one of those two things were to disappear, Honda would have to do some SERIOUS rethinking over the next 3-5 years as Honda's would certainly lose their lustre.
This is where American cars were/are a few years ago. The looks went down the toilet for most American cars and reliability (generally) wasn't that great compared to the Asian cars. MPG wasn't horrible but it wasn't stellar either. So...the American carmakers had to do some radical changes just to create (they hoped) excitement in the brand just to get the public to LOOK at them again (Z06, Viper, (Maybe) new Camaro, Charger/Challenger, GTO...and yes, even the various Hybrids). The problem with this approach, is that if you have nothing to sell to the other 95% of the public who don't want/can't afford those relatively few cars, it won't mean squat.
So, it's not so much a case of bringing out TOTALLY new cars every 4-5 years, it's bringing out cars that have more than one major category appeal. Honda really needs to look out as they seem to have become complacent (but who knows what they have up their sleeves), and IMHO are in danger of becoming another NISSAN in the next 10 years or so.
Toyota has nailed the Reliability category and seem to be doing well with the MPG wars but they too are VERY boring cars. BUT, they have NO real sports cars to create excitement and their cars are VERY boring to look at (I own an '04 Carolla so I know first hand). Toyota is about to take over GM for market share but they really need to rethink the outward design of their cars and need to add an affordable high-performance car (around 25K) that breaks the 6.5 second 0-60 range and could be offered as a drop-top. It wouldn't hurt if they paraded some sort of supercar at the car shows.
Anyway....this is all just my opinion (as flawed as it may be).