Viktor is an increadibly strong mage and has the potential to shine in every game.
There are very few bad matchups and even in those you have the potential to be a strong opponent.
For me what makes Viktor so interesting to play is the basic skill within the game that allows you to perform good on Viktor. By that i mean, that as Viktor you need to learn lasthitting, wave-management, map awareness, mechanics, movement and other basic principles that you can apply to other Champs aswell.
The reason for that, is that in order to get into the part of the game where Viktor is really strong you have to get through the laning phase, while still farming successfully to stack your passive. Even if you do that however, you wont get far as Viktor if you dont show some mechanical skill and understanding of the game.
For me personally, playing Viktor allowed me to reinvent my playstyle and learn new approaches to the game even, when playing different champs.

Therefor, if you are looking for a mage to play in the midlane, Viktor might be the pick for you :^)