A Team To rate.

[Eruption]

My Leaf Green team that has 8 Badges but has not Done Elite Four

Venusaur Lv51
Item/ None
Moves/
Strength Cut FrenzyPlant GigaDrain
Nature/ Mild

Butterfree Lv45
Item/ None
Moves/
DreamEater SleepPowder Flash PsyBeam
Nature/ Modest

Zapdos Lv52
Item /None
Moves/ Fly RockSmash Detect DrillPeck
Nature/ Lonely

Moltres Lv57
Item/Amulet Coin
Moves/
FireSpin FireBlast Fly Flamethrower
Nature/ Mild

Snorlax Lv46
Item/ Cleanse Tag
Moves/
SolarBeam Surf SleepTalk BodySlam
Nature/ Sassy

Articuno Lv59
Item/ None
Moves/
Mimic HyberBeam Protect IceBeam
Nature/Jolly

 

[Demonta]

You will be able to beat the league easily.

 

[Eruption]

Nope I been trying to do it 4 ages.

 

[Lathspell]

This is how your team should look like.

My Leaf Green team that has 8 Badges but has not Done Elite Four

VENUSAUR @ Leftovers
Overgrow

Sludge Bomb/Sleep Powder
Razor Leaf
Sleep Powder
Synthesis/Leech Seed

BUTTERFREE @ Quick Claw/nothing (not worth leftovers)
Compoundeyes

Sleep Powder
Stun Spore/Supersonic/Toxic
Silver Wind/Psychic
Thief/Protect/Substitute (Filler)

ZAPDOS @ Leftovers
Pressure

Thunderbolt
Rest
Drill Peck
Thunder Wave/Light Screen

MOLTRES @ Leftovers

Fire Blast/Flamethrower
Sunny Day
Toxic/Rest
Aerial Ace

Moltres doesn't learn too many good attacks...

SNORLAX @ Leftovers
Immunity

Return
Shadow Ball
Earthquake
Rest

Curselax is better, but you probably don't want to breed for Curse, so use this one.

ARTICUNO @ Leftovers
Pressure

Ice Beam
Sheer Cold
Mind Reader
Rest

Ingame, the Mind Reader + Sheer Cold combo beats anything in 2 turns, since the opponent never swithches.

You probably don't have more than two Leftovers so use one on Snorlax and one on anyone else except Buterfree. Buterfree is really lame, if you could get something else, do that, maybe a Rhydon, and use this on him:

RHYDON @ Choice Band/Leftovers
Rock Head

Earthquake
Rock Blast/Rock Slide
Double-Edge/Swords Dance
Megahorn

Choice Band if you can't breed Swords Dance, else, Leftovers.