I visited them the wrong way around, I now notice: the "youngest" temple first. This one is at Tarxien, in the town of Paola (close to the Hypogeum). It looks like you're in someone's backyard, but there are really fine features here. For example the animal reliefs.
On the other side of the island are the temples of Hagar Qim and Mnjadra. The Mnjadra temples have the most beautiful setting, near the sea and the islet Fifla.
After that, I went to Gozo island to visit the Gigantija temples. Less refined, bulkier than the others they are. A visit to the archeological museum in Valetta to see the more delicate findings finished it all.