"Best" is probably in the eye of the beholder.
If were were just talking "long guns" then the British Army Brown Bess musket, as it probably was responsible for concuring most of the known world at the time.
I would concur that other "rifles" would need to include the Mauser Action, the Lee Action, the MN action.
The US Springfield and the Japanese Arisaka are also impressive bolt action rifles.
For semiautomatics the M1 Garrand, the M-14, M-16, SKS, AK-47, and M1 Carbine were all made in substantial numbers.
A friend recently rescued two Arkisaka rifles from his father's closet. I helped him clean up the Model 38 in 6.5mm. It is amazing how firm nearly 60 year old cosmoline can get. After soaking the bolt for two days in Ed's Red; plugging the barrel and letting it soak for two days in Ed's Red; I got around to taking things apart and cleaning several decades of neglect.
Wow, did it ever clean up nicely! I took the bolt all apart and was impressed by how much cosmoline was still hidden in it and by the simplicity of design.
The Arisaka model 38's were nice rifles, although I really like my MN1891/30.