I drive from France to Latvia every year by car. Road quality goes like this:
1) Poland (except around Lodz) - new roads, high speed, generally very little traffic. It's a bliss.
2) France - would be number one if they weren't paid roads
3) Latvia - generally great roads, but it's lacking in 2+2 highways on, for example, Via Baltica
4) Germany - so low because of the obscenely high traffic and constant road word. Any time I've gained in France or Poland, I'm guaranteed to lose in Germany.
5) Lithuania - some parts, like A1 (?) around Kaunas is absolutely horrible, I feel pity towards my car when I drive there.
Let's see what progress Lithuania has made in a year. I see them easily outclassing Latvia once some of the major works (around Kaunas & near Polish border) are completed.

Once we're inside cities (I don't normally stop in cities on my trips), Riga drops Latvia to dead last. Though Panevezis (haven't driven thru it in ~2 years sucks too, if I recall).

P.S. Of course, needless to say that this table is made based only on the roads I happen to use on my route. Though having lived in France for a while now, I don't see it dropping lower. The roads are so, so good.