I can't tell you what to pick but I guess I can play devils advocate with the other choice.
Side with the mages- Most of the mages had rebelled and/or became possessed. How can you be sure to control them on the battlefield? It could be logically to recruit the Templars, although some died at the tower, they were waiting for reinforcements which you can use for the Blight.
Save both Connor and Isolde- To save Connor you had to travel from the house and leave him unattended thus endangering the lives of his mother and Tegean. A warden who wishes to save as many lives as possible may deem it necessary to end the boy's life.
Kill cultists- The cultists offered a peaceful solution for you and your companions along with more power to fight the archdemon. As Morrigan says, if you spare them, you will have these men loyal to you which is a bonus. Also, leaving the ashes pure allows everyone in Thedas to come along and take advantage of them, which they do.
Reveal ashes- See above. It does more harm than good.
Cure werewolf curse- I usually pick this one too, but if you need a reason to go against it. The wolves were attacking those bound to be your allies, someone of the Keeper's age could be vital in keeping your elvish allies more stable than killing him off and leaving a young keeper in charge. He may also provide old knowledge and power just in case the Blight get's worse.
Destroy Anvil- Orzamaar has been fighting the darkspawn for centuries. Caridin has his reasons to want it destroyed but at the same time it doesn't seem like he's been fighting the darkspawn lately. Not only can the golems help secure the deep roads but help the surface in case things get worse.
Crown Bhelen- No devil's advocate here as I love this option, i can't think of any reason to crown Harrowmont. lol!
Put Alistair and Anora on throne- If your warden is a Cousland man then perhaps he would be more useful on the throne than a man who refuses to lead at it's darkest hour. If Alistair isn't hardened then I worry even more about putting him on the throne, especially after how he carries himself at the landsmeet if you spare Loghain. Anora seems to do the job on her own.
Spare Loghain- I like this option too. I thinkt he more Paragon option is to kill him.
Do the Dark Ritual- no complaints.
Save Amaranthine- Perhaps burning the city is better. When you get there everyone is diseased or dead. Not only that but burning the city strengthen the Warden's and cements their place int he country.
Kill Architect- Keeping him alive means that the darkspawn can be reasoned with, form alliances, and so on. Killing him keeps the darkspawn as mindless monsters who can be lead by a single beast.
Hope that helps in some way.