I suppose it depends on what purpose and at what point of the war. I'm not going to bother much with tech specs. You can find them anywhere.
The YAK-9 was a corker of a plane. Entered service at the end of '42 over Stalingrad and was rightly feared. Variants were too many to list but included a tank-buster (37mm centreline cannon - like the P-39). The Russians used it almost all alltitudesd according to variant type.
The YAK-3 was a tidy little piece as well. Despite the service number it came in after the YAK-9 (July '43). Cheap, cheerful and very nimble. Probably a tad under-armed but had a good kill-ratio.
La5 and La7 came from a flying pig (the LaGG3) but earned a tough reputation. Twin 20mm cannons and a rocket rack option made them something to worry about.
The Ilyushin (IL-2) the Sturmovik was a beast (entered 1939). Designed specifically for low-level ground attack it was an armoured rhino and very hard to take down. The crew was protected in a bathtub shaped armoured shell. Later marques had a rear gunner. From memory it was the most produced Soviet plane during the war.
The Ilyushin DB-3 was the the Dakota DC-3 equivalent only with guns. A jack of all trades and often forgotten. Very handy plane (but not for a dogfight!)
I'll leave the Polikarpovs and other biplanes alone but if anyone wants to add something, they're more than welcome. Wiki them up, it's easy.
Overall, The Soviets' determination to swing stuff into service was incredible. Their design ethic was to fix on a workable design, improve it and produce a limited range but in huge quantities. Combined with Lend-Lease equipment like Hurricanes and P39s and so on they were a very dangerous air force.