The previous answers cover most of the popular fighting games of today, but let me give you a more personalized answer.As you used to enjoy Street Fighter 2 and Tekken (I assume Tekken 1,2,3), you can try out the latest crossover game called "Street Fighter X Tekken". However, that game follows mechanics derived from Street Fighter IV, which is again somewhat similar to Street Fighter 2.Street Fighter 3 and the Alpha games took SF gameplay to different levels, but SF IV tried to go back to the roots. So you will find yourself at home with Ultra Street FIghter IV, too. It is one of the most balanced fighting game out in the market, and the game is in its final version after a number of updates in the form of SF IV, SSFIV, SF IV AE and fiinally, USF IV.These two games are available for PC, so if you own a decent gamepad and no console, you can go for it. An Xbox360 gamepad should suffice, as it is a very good gaming device for anyone who just wants to enjoy their game without bothering too much about serious competitive gaming.As for Xbox360 and PS3, there'd be hardly any difference in performance if you have a good internet connection.If you just want to enjoy raw Tekken mechanics, you can go for Tekken 6, which is a solid and robust Tekken game. It has most of the old favorites like Jin, Hworang, Paul as well as interesting, new brawlers, However, you can also wait for Tekken 7 which should be released sometime this year, or you can wait for the "Tekken X Street Fighter", which will be a new crossover game (Not to confuse with SF X Tekken) where Tekken mechanics will be used. This game comes out in 2013, so it'll be a long wait.If you want a simpler fighting game to start off with, you can go for Ultimate Marvel VS Capcom 3. This game is easy to learn, and even the beginner player can pull off ridiculously damaging combos. This game is a sequel to MVC2, which was very popular back in the days of Sega Dreamcast console. It's a crossover of marvel characters (X-Men, Spiderman, Iron Man, etc.) and Capcom characters (Street Fighter cast, final fight, captain america, etc.)As for Mortal Kombat goes, the latest game in the series (simply called Mortal Kombat or MK 9) is brilliant; the campaign will take you through a re-telling of the events that took place before the first game in the series. The campaign itself justifies playing this game, and the multiplayer action is also a blast (both offline and online)I really won't recommend the latest King of Fighter games as they are absolutely rubbish, and any other fighting game series won't be worth your time, except maybe the latest Soul Caliber game.Kof XIII is quite decent, though. Still not as great as the older games, but worth playing if you loved the past games or are interested to get in to the series.As you will be returning to fighting games after a long time, the most striking difference you will find is more reliance on damaging combos instead of poking styled fighting.Nothing beats the arcades, but today's online match ups aren't bad either.Happy gaming
