Amici's definitely wouldn't make my top 5 in Los Jardines, let alone in Santiago...overrated and overpriced, with possibly the slowest service in town, IMO....not bad, just not that great...for really good Italian food with great atmosphere, I'd chose Pasticcio's, or also in Los Jardines, Il Toscano, over Amici's any day....
For great value, usually lively atmosphere (outdoors), and good food, I'd add Zokalo Mexican...in Plaza H2O, maybe not in the "best of Santiago" category, but one of my favorites.
For real "High-End" dining, I'd choose Tete Club (Calle Sol, near Monument), Satay (Av. 27 de Febrero), Pedro's (Los Jardines) or La Marquezzina de Paparazzo (Just off Jon Pablo Duarte). For cool and trendy, I'd choose Front Door (Los Jardines).
And my choice for best Full Menu Chinese restaurant (food, decor, service) is Super Rico at the end of John Pablo Duarte. There are several surprisingly good Chinese restaurants in Santiago though...