Gaudy, tawdry, garish, flashy, meretricious are comparable when meaning vulgar or cheap in its showiness.
Something is gaudy which uses gay colors and conspicuous ornaments or ornamentation lavishly, ostentatiously, and tastelessly.
Something is tawdry which is not only gaudy but cheap and sleazy.
Something is garish which is distressingly or offensively bright.
Something is flashy which dazzles for a moment but then reveals itself as shallow or vulgar display.
Something is meretricious which allures by false or deceitful show (as of worth, value, or brilliancy).