Where is the best fondue in Geveva?

Sorry, I cannot give a recommendation for Geneva.

But I have eaten a most spectacular seafood fondue in nearby Montreux (of course, they also serve meat fondue and cheese fondue).

It is a spectacular experience because they serve a container with smouldering charcoal on your table.

The ambiance is very romantic, prices are more than reasonable.

Caveau des Vignerons

They do not have a website, but here is a description:

http://www.frommers.com/destinations...ux/D49279.html

Is fondue a 'year round' dish, or mostly/only for cold and winter seasons?

Fondue is normally speaking for the colder periods. However, it is served all year round, and not only in tourist places. I do occasionally have a fondue in late spring or early autumn when the weather is still fine. You'll find, e.g. in tourist places such as Gruyeres, fondues served in summer on the terrace.

There are quite a lot of different fondues, according to the canton where you are or to the inventiveness of the chef. You might find fondues with tomatoes, with mushrooms, with different mountain herbs,...
The most commun fondue in Switzerland is the 'moitié-moitié', meaning half Gruyère cheese and half Vacherin, melted in white wine at a rather high temperature.
The Fribourg favorite would be the Fondue Vacherin, 100% vacherin cheese, warmed at 50 °C, in the 'caquelon' (the pot) frotted with a clove of garlic. No wine in this one, only water. Very creamy and easier to digest than the moitié-moitié. A bit more difficult to make, as the vacherin 'turns' when heated over +- 55°C.

I can't answer the OP's question however; I am living in Vacherin Fondue Country...
A moitié-moitié to me is very close to heresy, all different varieties definetely are.

There is much more than cheese fondue:

- fondue bourguignonne: you cook meat in oil

- fondue chinoise: you cook meat, seafood or vegetables in broth

- Bacchus: you cook meat or vegetables in white wine

- fondue piemontese: melted butter, eggs, milk with white truffles

- chocolate fondue: fruits are dipped into melted chocolate

Les Armures

http://www.hotel-les-armures.ch/en/g...restaurant.php

More of a winter dish, but served year-round. Sorry don't know Geneva. There's a nice place in Vevey ;-)