This is a special year for Pokémon fans - 2021 rings in the 25th anniversary of this world-conquering franchise, two and a half decades since the release of the original game on Nintendo's Game Boy.

Since then there have been countless spin-offs, movies, TV shows, an enormous card game, and more merchandise than a Farfetch'd could shake a leek at. Through it all, though, there have been the main Pokémon games, steadily expanding the roster of monsters and introducing us to new lands.

We've brought them all together here to celebrate how far they've come - check out every mainline Pokémon game to see how they've changed through history. 

Pokémon Red, Green, Blue and Yellow

The first generation of Pokémon games were a revelation, but also a bit complicated. In Japan the first to release were Red and Green, but Blue came swiftly afterward with some improvements. Red and Blue then made their way to the rest of the world with some small differences between versions. 

A couple years later, Yellow came out as the definitive package, letting you collect more Pokémon, foster a connection with a grumpy Pikachu, and making it way harder to cheat (spoilsports!). The original 151 Pokémon from these games are still the most iconic of them all.

Pokémon Silver, Gold and Crystal

With the Game Boy Color, the Pokémon series burst into colour, and Silver and Gold are still the absolute high watermark of the series in our minds. Expanding the formula with a new swathe of brilliant creature designs, and a new world to explore, they're moodier and rewarding.

Plus, in one of gaming's great twists, finishing the game let you revisit the world from the last-gen games all over again as an expansive endgame challenge, culminating in the series' greatest ever fight, against Red himself in Mt Silver. Crystal came along a year later to tie it all together.

Pokémon Ruby, Sapphire and Emerald

The Game Boy Advance brought new graphical fidelity to the table, and Pokémon leapt aboard with Ruby and Sapphire, followed by Emerald enhancing them further. 

Another new land beckoned, along with all-new monsters to collect, and new movement options including running made things a little zipper. The world design was gorgeous, while Groudon and Kyogre are two of the most memorable legendaries to front games in the series. 

Pokémon FireRed and LeafGreen

The Game Boy Advance also welcomed a new staple for the series in 2004 - remakes and re-releases. These re-do's of the first games in the series brought them to new generations of players and made them far easier and more convenient to play.

They'd be the best way to play the first game through for years, until a more recent release on the Switch, and really capture the joy of those first releases. 

Pokémon Diamond, Pearl and Platinum

The Nintendo DS is a beloved handheld for good reason, and it brought in an era of 3D graphics for Pokémon, and signalled a move away from sprites (which some mourned). Battles stuck with these beautifully drawn versions for now, though.

Diamond and Pearl were superb entries to christen the DS with, though, along with their tie-up version, Platinum. In fact, these games have earned remakes coming out later this year, Brilliant Diamond and Shining Pearl. 

Pokémon SoulSilver and HeartGold

Next up, it was time to give Silver and Gold a lick of new paint, letting players experience the fun of searching for Ho-Oh and Lugia themselves without needing to dig out a Game Boy to do it on.

The result are superb nostalgia-fests that let you play through your best memories without any of the rough edges that you might have overlooked. 

Pokémon Black and White

Black and White are interesting Pokémon games for a few reasons, not least that they make the story of the game a bit more of a focus compared to some earlier entries. 

It also cut itself off from previous generations entirely, featuring a fresh roster of monsters and no old hands at all - a bold play that its biggest fans found really refreshing. 

Pokémon Black 2 and White 2

The only linear sequels in the whole series - that's the major distinction setting White 2 and Black 2 apart. They pick up directly a few years after the events of the first games, and continue the story.

That made them interesting for fans, and if you liked Black and White there was no downside at all. They also let a few more old Pokémon join the party so things were freshened up there as well. 

Pokémon X and Y

The 3DS has an astonishingly good library of games, and its beefier graphics saw Pokémon again transition further toward full 3D modelling and away from 2D art.

These games brought that change to battles for the first time, making them a huge milestone for the main series, and while things have got more detailed since then, you can still see how important X and Y were. 

Pokémon Omega Ruby and Alpha Sapphire

Continuing the tradition of remakes, Ruby and Sapphire were next up on the 3DS, getting a major new lick of paint and again making it easier for new players to experience one of the older stories from the series.

Pokémon Sun and Moon (and Ultra versions)

Bringing tropical flair to the party, Sun and Moon (and their later Ultra upgrades) were super fun new entries that saw players exploring the Alola region, heavily modelled on island cultures. 

There were new cute versions of familiar Pokémon to find, and an enjoyable story to power through on your way to filling out that all-important Pokédex. 

Pokémon: Let's Go, Pikachu! and Let's Go Eevee!

With the Nintendo Switch, Pokémon was one of a few franchises to get a huge boost graphically. It went from being portable-only to a home console game, and the Let's Go games were a great way to bridge that gap.

These are more remakes of the very first games in the Pokémon series, but with some new mechanics like easier catching, and a totally new look that's completely adorable. It makes these the perfect games for newcomers to Pokémon.

Pokémon Sword and Shield

The most recent mainline games in the series are also on Nintendo Switch - Sword and Shield let players explore a land modelled heavily on the UK, collecting new monsters as they go.

Its major expansion pass signals another new frontier for the series, and suggests that the games might not get the standard re-release with some upgrades - there's no need, thanks to DLC!