ok, I may see it differently, because I was born here, and these are just opinions just like everyone elses.... but in my view, if it´s main roads we´re talking here (highway 5 & 6), they´re rather boring and straight. Lots and lots of woods, some lakes and tiny villages - and may be they appeal to a tourist, I dont know.

To me, most fun and scenery is to be had on the smaller, more curvy backroads, preferably the ones that have 3 digits in their number, or even 4 (the condition of those last ones may not be so good, especially after last winter, which was unusual). Sometimes there is no asphalt, but with some caution the surface usually remains ok to ride even with a streetbike. A navigator with up-to-date map data is your best friend on small roads - if you have some more specific idea, which way you want to go & time frame, I could suggest some routes to take?

But if you dont have much time, then you may have to stick to the highways. In general, eastern part and northern part of Finland are probably more scenic than the flatter south and west. The lake district is probably something one should not miss, and the reas around Kuusamo, about 800kms north/northeast from Helsinki are also a highlight. But beware of moose everywhere here (there have been accidents with them near Helsinki just days ago - and some happened in broad daylight!), and also reindeer in the north!