1. Capcom vs. SNK 2 - This was my go to Street Fighter game for the PS2 era, still play it now and again with friends.
2. Street Fighter III: 3rd Strike - The reason I bought a Dreamcast and an Xbox, we didn't get it on PS2 in the UK.
3. Street Fighter Alpha 3 - My go to Street Fighter game from the PS1 era. I wish they would do a modern Alpha collection with online play.
4. Street Fighter II: Turbo - The SNES port is still one or the best home versions of Street Fighter in my opinion. It just feels so good to play.
5. Ultra Street Fighter IV - The ultimate version of the game that saw the re-birth of fighting games.
I should add Street Fighter V really. I think the fighting game at its core is so good I could cry, just the game built around it needs a lot of work.
Here's a video of my Street Fighter collection pre SFV...