I don't really count the Stones among my all-time favorite bands - but I like them a lot, and know their music very well, used to listen to them a lot. In my opinion (agree with Rock Action & others) they came into their own during the period when Mick Taylor joined them - it wasn't just Taylor's own fabulous guitar-playing, the collaboration just brought out such great things in Keith as well. Let It Bleed was an incredibly strong album, and Get Yer Ya-Ya's Out, Exile and Sticky Fingers are all very good too. Leading into that period, Beggar's Banquet was pretty strong too.
The Brian Jones period, after they started writing their own songs, certainly has a lot of charm as well, but in a slightly erratic kind of way I feel. Their Satanic Majesties Request is a good example: there are wonderful songs on that album, but the arrangements to me are not - psychedelic Stones don't sound very convincing to me. Aftermath has a great many good songs, but it's like thy're still struggling trying to find their own direction in their own songwriting - which is hardly unnatural.
Speaking for myself anyway, generally the Stones were a damn good band - but never as good as The Beatles or The Who, let alone Led Zeppelin.