Verified answer

I'll rate each individual pokemon for how they fit in a competitive pokemon environment, then I'll rate your whole team. *this team rating assumes all your pokemon are EV trained, and have the correct nature.*

1. Magnezone- 2/10. I'm sorry, he just isn't very good. What's the point of TWO electric moves and TWO steel moves? Steel is very poor offensively and not worth having, usually. He needs to know Thunderbolt instead of all those moves you had. Thunderbolt is a MUST for Magnezone. None of the moves you have can be allowed. In competitive battling, all you need is one move of a certain type on a pokemon, not two, because there is simply no purpose for having two. You won't run out of PP. A few possible moves would be Magnet Rise (good defensive tactic), Explosion (good finisher), Substitute (good defensive tactic), Flash Cannon is OK I guess, and hidden power is excellent (but only if it is the type ice, grass, or fire.). Make sure you do not have two moves of the same type! Also, make sure his ability is magnet pull (you can kill off steel types.). If he has just attacking moves, give him a choice scarf. Otherwise, give him leftovers.

Steelix- Forget him, pick magnezone instead.

Blissey- Deecceennntt... 6/10. All blisseys want Seismic Toss, and if that's not possible for you (I think it only learns it by move tutor in Leaf Green and Fire Red..), It needs two of these- Thunderbolt, Flamethrower, or Ice beam. Protect is a very very nice thing to have, and wish would cure pokemon other than blissey because it heals at the end of the SECOND turn. Its an option if you want blissey as a supporting pokemon, but as a wall, you want blissey to have softboiled. Toxic/Thunder Wave are musts, and you have Toxic. Excellent! Softboiled/Wish is a must, you have softboiled! You just need to add two of those four offensive moves I gave you (Seismic Toss, Thunderbolt, Flamethrower, Ice Beam) and your blissey will be great! Make sure her ability is Serene Grace! Also, give her leftovers as an item to heal her steadily.

Staraptor- Mehh.... 5/10. Brave Bird, keep. Close Combat? Keep. All the others? No! Give him a few of these moves- U-Turn, Quick Attack, Pursuit, Return, or Double Edge. Make sure you give him either a Choice Scarf or a Choice Band, because this is an all out attacking set!

Infernape- 5/10... Replace Flame Wheel with Flare Blits, Rock Climb with Stone Edge, Focus Blast with U-Turn, and keep close combat. Give him a choice band too!

Gyarados- 9.5/10 moveset here- Dragon Dance, Waterfall, Stone Edge, Earthquake. Give him a life orb, set up a few dragon dances, and your added speed and attack will beat anything (pretty much). Adamant or Jolly would be the best natures.

Garchomp- -5/10. Garchomp is BANNED from competitive battling!!!! Salamance is also. How about a choice banded Dragonite? Pick four of these moves- Outrage OR Dragon Claw, Earthquake, Waterfall, Fire Punch, Extremespeed. That would be really good! Make sure he is ADAMANT or JOLLY.

Overall, for competitive battling, I'd give your team a 5/10. It could realllllyyy use some work to compete. You should try http://www.smogon.com/ is pretty much the only site for competitive battling. Also, for a lead pokemon you want something with spikes and or stealth rock. Trust me, it may seem bad, but SR and Spikes can completely destroy a team that loves switching.

Hope I helped! :)

Magnezone, steelix and gyrados will get slaughtered easily. I'd answer if you listed your EV distribution and natures, maybe IV's. garchomp needs sword dance, crunch or stone dge, fire fang, 2 of those 4.