There seemed to be a huge amount of quests in whiterun, riften and winterhold not so much....I haven't explored the other main towns yet.

Are any others as full of content as whiterun, or are they more for the guild quests?

Thanks!

Most guilds/faction are spread across the towns, Thieves guild is in Riften, Legion is in Solitude etc... all towns are filled with quests. Personally I love Solitude the most, it's the capital, it's my home, and I there are so many things to do there...

Riften has a bunch, but not quite Whiterun-level.

The biggest (non-faction) places ought to be:
Whiterun, Solitude, Windhelm, Riften, Markarth

Winterhold, Morthal, Falkreath, and Dawnstar each really only have a handful each (if one ignores the faction quests in Winterhold).

Simple: walled towns > open ones, in terms of content.

Well Winterhold is pretty small compare to other major cities, so naturally there are less to do. But rest assured, once you explore the other cities, there are plenty of excitement waiting for you. My favourite so far is Solitude as well, being the capital makes a huge difference.

Brilliant guys thanks!

solitude is the capital?

Yeah Solitude is the capital of Skyrim, because of it's Imperial base and Skyrim being Empire-controlled in 4E200.

Also, I was VERY disappointed with Dawnstar and Winterhold etc. They're not towns at all, they're just villages. Haven't been to Solitude yet.

I understand that Skyrim has far less inhabitants compared to Cyrodill but still.

I like whiterun, it seems to have the most functional market to support my adventuring. You walk in the gate and can sell armor/weapons to the blacksmith outside, if she runs out of gold go inside and sell more to her husband. Then your house is right there next door, basically a forge shop in your back yard. Then right past that you have an alchemy shop and general store, can't beat it as far as I've seen. You go to any other city and it's harder to find the shops. Even Solitude the capital pales in comparison to Imperial Cities market place. I know it's not IC, but come on man, this game is 5 years older there should be more shops, more people in the capital of skyrim than in IC market place.

I haven't spent enough time in the other towns yet, so I don't know my way around so maybe there are better stores I just don't know about, but to me White Run is the main hub of the game and the best city. Solitude is full of snobs. It's bigger but to me it appears to have less content than Whiterun.