Aperitivo/Cichetti in Milan?
Good is pretty subjective. It really depends what you are looking for. Do you want a drink and some snacks before moving on? Do you want to substitute for dinner? Do you just want to people watch? Aperitivo in Milano can be all of these things....
Here's a few places I like for various reasons:
Bar Brera--via Brera 23
Bar Brera offers an extensive drink list filled with classic cocktails. They offer a large selection of hot and cold dishes as well as sweets. However, the best reason to visit Bar Brera is for the unending parade of both arty kids from the school of the Pinocateca Brera and fashionable Milanese. The only drawback is the large amount of second hand smoke you will inhale thanks to the tightly packed tables.
Moscatelli--Corso Garibalidi 93
Depending on when you arrive the food may be scarce. They don't always replenish it quickly but there is usually a respectable variety of meats, cheese and focaccia. There are good wine selections by bottle and glass. Outdoor seating.
Gold Cafe--Corso Garibaldi 89
If you want your aperitivo to be more about eating than drinking, this is the place. There is an absolutely gigantic buffet that is genuinely superior to most others. Lots of hot food with pasta, chicken, and seafood. You can substitute for dinner here.
Obika--Via Mercato 28
If you like cheese, this is the place. It is not the most characteristic of aperitivo but the food is pretty good and the place is popular for a reason. It's also pretty expensive for aperitivo, I think it was 12 euro the last time I went.
Da Claudio--Ponte Vetro 16 A few doors down from Obika in Brera. This is a fish market that also offers a raw fish aperitivo. Think ceviche and you're almost there.
There are aperitivo all over town but the above are within walking distance from the Moscova or Lanza metro stop on Milan's green line.