There are always some "trendy" styles that differentiate professional creations from amateur ones. CollegeHumor made a parody of professional-looking trailer for fictional movie Minesweeper [en] and LIMO cabaret did the same with movie Leszek Balcerowicz - Nieznana historia [pl].
What about games? Today people I'm following on Tweeter posted interesting links about graphics in modern games. First, this comic says much. Dark, brown and gray colors are common in today's games, especially in some genres like action games (opposite to colourful fantasy RPG and arcade games, like Trine). Here is also a funny picture. Second, Kayamon posted on his blog quite serious note about how render target size can be reduced by using only two channels to describe pixel colors. His experiment gave quite good results with screenshots from Gears of War :)