I have to concur with the Golden Age being in the 50s and ending in 1969, September 26, 1969 to be exact, when NBC canceled The Match Game, Eye Guess, You Don't Say, and Split Personality.
I definately also agree with the Silver Age starting in 1972 with the premiere of The Price is Right. My reasoning is that TPiR was only one of three shows from the Golden Age that was given a complete makeover which made it better than the original (the other two being Match Game and Password).
Where I disagree is that 1980 (6/20/80) marked the end of the Silver Age. Rather, it ended Phase I of the Silver Age, with Phase II beginning September 20, 1982 with the premiere of The $25,000 Pyramid (Match Game ended its 9 year run over a week prior). This also more or less kicked off the era of daily (as opposed to weekly) prime time game shows.
Phase II almost died off in 1989-90 with the ending of Super Password and Scrabble, but the 1990-91 season gave Phase II a final brief burst of life with a series of revivals (TTTT, $100K Pyramid, The Joker's Wild, Tic Tac Dough, Supermarket Sweep, and the Challengers) and a few original shows (Trump Card). Once that season ended, Phase II ended with it.
Considering the game show choices you had (Caesar's Challenge, Born Lucky, Quicksilver, Free 4 All, Debt, Shop Til You Drop, FF '94 with Richard Dawson), the 1990s were pretty much The Dark Period of game show history.
In 1999, the bronze age came about when WWTBAM aired on ABC in prime time, with Twenty-One following suit on NBC.
So as far as the 2000s being the styrofoam era, well I wouldn't say that we're in the styrofoam era, but I do remember Dennis Miller saying in one of his rants that we have gone from the GE College Bowl to contestants on Wheel of Fortune saying, "I'd like an F as in pharoah."