I'm pretty casual and I like lot of them. Not sure I have a truly defined favorite series but I like almost anything from Capcom/SEGA and SNK in the 90s. I lean more towards Capcom stuff of the era. Tho I loved VF2 in arcades. I liked MK 1-3 and UMK3 after that it's major hit and miss. I think Arc atm is the best at the genre. I like Smash for the rosters.
I think my fave might be Virtual On going by what I tend to gravitate towards. I'm not some expert player by any means but it has mechs ans those mechs have Saturns/Dreamcasts on their backs. Plus they play almost like an action game with melee,grenades,shooting and specials but it's confinred to an arena. I like VO so much I buy games that remind me of VO. Senko no Ronde 2 (which even has Temjin and Assault Suit Valken DLC) Frame Gride developed by From Software. ARMS by Nintendo. Gundam Versus and Maxiboost. Of course other enties in VO itself.