As long as you have a friend who is a fan of Tekken, or fighting games in general, you'll have a blast with Tekken 4.
Of all the shortcomings, the most disapointing would be that the game lost some characters. However, the characters that it lost have similar counterpart characters with similar movesets. For example, Forest Law from Tekken 3 was removed but Marshall Law took his place and fights just about the same as Forest. There are also some entirely new characters to be found. The first one is Craig Marduk who is a Vale Tudo fighter. He is big and tough but not so quick. The next new character is Christie Monteiro, the counterpart of Eddy Gordo from Tekken 3 except a female. Her fighting style is Capoeria. The last new character is Steve Fox who is a British boxer. Those were just from the normal already available characters so expect to see plenty more unlockable characters. Tekken 4 keeps all the core characters from the past game like Jin, Hwoarang, Xiaoyu, Paul, King, Yoshimitsu, Kazuya and more but also adds these new characters so you won't get tired of playing as the originals.
Now in the gameplay department, the game sticks to the same fighting game formula from the past games however the opponent A.I. this time around is a bit smarter. The game has the same difficulty settings ranging from easy to hard to ultra hard. There are plenty of settings so if you're a beginner you'll feel right at home but if you're a huge Tekken fan then you'll know what to set the difficulty to and expect a challenge. The game controls great too. You use the D-Pad and the buttons so it feels just like any other Playstation 2 fighting game and there are plenty of combos. There are a lot of combos for each character so the game feels really advanced in that category.
Just like every other Tekken game there is a side game in Tekken 4. It is called "Tekken Force." In Tekken Force you are basically sidescrolling through a level and constantly beating up enemies that come near you. There are tons of enemies and when you make it to the end of that level there is a boss waiting for you at the end. The boss battles are the characters from the main Arcade/Story modes of Tekken 4 so don't expect crazy bosses. So besides Story Mode and Tekken Force, the main mode that will stick out to you is the Vs. mode. Yes, of course there is a Vs. mode and it is the best aspect of Tekken 4. You go head to head with a friend to see who is the best. Things just don't get much better than that. Plus, you can try out the new characters of Tekken 4 against each other to see who is the best.
From a visual standpoint, Tekken 4 shines without a doubt. There are a few touches keeping it from a perfect ten and i'll get to those soon but I'd like to start with what is good about the graphics in Tekken 4. First off, if you've played Tekken Tag Tournament, Tekken 4 looks much better. For it's time T.T.T. was something but now Tekken 4 dethrones it. Even by 2006 standards Tekken 4 stays with the crowds but looks a little bit outdated. The best aspect of the game in the visual department is probably the backgrounds. Each stage has a different background like a jungle or an airport and these are incredibly well detailed. The character models also look jaw-dropping. One gripe I had was that in the cutscenes sometimes the voices don't match with the mouths moving. But the game runs smoothly and the animation is great. The new characters were well designed.
Moving onto sound. The music in Tekken 4 ranges but most of it seems more techno or trance-ish. The music is great but where improvements could've been made is the voice work. I'm not saying that the voice acting was bad because most of it is good but you can notice some funny parts especially in the cutscenes. Some characters have downright terrible voices while others have great ones. Also, Hwoarang who is supposed to be Korean talks in a really English voice sounding just like an American. Jin however sounds more Japanese even though his voice is in English. He is supposed to be Japanese. Some characters have been dubbed.
This game provides quite a bit of replay in the single player with Story mode and Tekken Force mode because in Story you'll have to beat the game with everyone to unlock everything. There are cutscenes and characters to unlock so it'll take a bit. There is no online play to be found in Tekken 4 which would've been a nice feature. However, the 2 player battles are loads of fun and will last you a long time. As long as you have a friend who is a fan of Tekken, or fighting games in general, you'll have a blast with Tekken 4.