i don't think anyone owning a wii will miss out on the cool games. siguro sa case dati ng ps2 naiiwan talaga ang ibang consoles because some game developers, the best ones at that, made games exclusively for the ps2. pero ngayon, sony has lost that exclusivity and the developers are crossing over to other platforms as well.
also, the definition of a "cool game" is subjective. depende sa gamer kung ano ang habol nya. if he/she gets off on stunning graphics more, better get either the ps3 or the 360. pero if he/she can live with so-so visuals BUT more enjoyable experience (<= emphasis on the word), then the wii is the best way to go.