Really enjoyed the graphics of Secret Files: Tunguska.
Is the game any good?
It's ok.
You can play it, but it certainly isn't a must.
Unfortunately, the graphics are the best part of the game.
Some of the puzzles didn't make much sense. And there is some serious pixel hunting in there - so the Hotspot cheat button is kind of necessary in some scenes, if you aren't lucky.
They also didn't know where to go with the story. It's starts kind of interesting with the Tunguska incident, but then meanders into Russian mafia, a secret cult etc.
The original ending didn't resolve most of the story arcs. Lots of people complained, so the developer changed the ending completely and even rendered a new ending video that was distributed via a patch for free.
Unfortunately, the new ending didn't resolve anything either and even raised more questions...
And the whole story, questions and endings are completely ignored in Tunguska 2 - at least in the intro sequence.
I must admit, that I haven't completed the second game. So it might be, that the issues are dealt with later in the game - but I doubt it.
TLDR:
If you can get the first game cheap and like the graphics: You can give it a try.
Just don't expect too much from the story and the puzzles.