The Basics
As an all rounder and a very simple character, Ryu takes a lot of work to win with. There is very little surprise factor coming from Ryu at high level, since he's essentially the most standard and studied character in the cast. As a character, he has no major strengths or glaring weaknesses, but the lack of surprise factor and linear play style makes him a character that takes a life time to master.
In order to play Ryu well, you need to understand and accept that you'll put yourself in disadvantageous situations. He does not excel particularly in anything outside of zoning, but he will have match ups where his fireball game will be rendered useless. Even in match ups where your fireball game does stay effective, you'll never truly feel like you have a big advantage over your opponent. Likewise, in disadvantageous situations, you'll feel very uncomfortable and oppressed, so it's important to have lots of patience in order to play Ryu. He takes a lot of dedication and mental fortitude, but any player who can stay vigilant can and will make him work, even at higher levels.
That said, Ryu is a very easy character to learn. If you're new to the game, it's always a good idea to start out with Ryu. Even if he isn't particularly your favourite character, just having a pocket Ryu helps. When you play Ryu, not only do you learn about the character, but you learn the core fundamentals of Street Fighter. As you get put into bad situations, you force yourself to stay disciplined and patient, which can carry over to most other characters you can play. If you want to play a fireball zoning character, Ryu has the standard fireball and anti air game that you can carry over to other projectile characters. If you want to play a more footsie based character, Ryu's footsie tools are decent enough to help you carry the skills you practice to other characters as well.
Strategy
Mastering Hadoken
While Ryu is a jack-of-all-trades that can perform well at any distance, it should come as no surprise that his best position is long-range zoning, and learning how to implement his use of Hadokens at is critical to mastering Ryu. Unfortunately, this is much easier said than done.
Your main strategy as a Ryu player will be to capitalize on your opponent's mistakes, so make sure you watch your opponent's reactions to your Hadokens carefully. Inch forward if they decide to neutral jump over them (LP Hadoken is especially useful for this). If they take the risk of forward jumping, find out where they would end up landing and anti-air accordingly (St. HK from a distance and MP/HP Shoryuken point-blank). If they Focus absorb your Hadoken, watch for if they forward dash or backdash. If they forward dash, analyze whether or not they are entering mid-range, and stick out Cr. MK if they are. If they backdash, press closer toward mid-range and keep them in blockstun with more Hadokens or Cr. MK blockstrings.
The only difference between the three Hadoken stregnths is the speed that it travels; LP Hadoken travels the slowest, HP travels the fastest, and MP travels somewhere in the middle. LP and MP should only be used from a distance, as a slower Hadoken in a mid-range/close-range game will not benefit you in any way. EX Hadoken is a good option is you can predict your opponent attempting to focus absorb or just to get a bit of extra chip damage in.
In projectile wars, you should still be paying attention to how your opponent reacts to every Hadoken you throw. Watch carefully if they move forward or back to determine where they want to end up, and if they're skirting towards the edge of mid-range, be ready to intercept a jump. If you can decipher a pattern in your opponent's projectiles, a well-timed EX Hadoken can give you a big advantage whether it lands or not. If it lands, your opponent will have to recover from a soft knockdown, giving you a great window to press into mid-range. If your opponent blocks, they'll be stuck in blockstun for two hits, which still gives you a good window to press forward.
