I live in Burntisland which is a seaside town in Fife, Scotland.
So starting with my garden and street there would be:
Pet life - Assorted Meowths, Glameows, and Skittys... depends on the type of cat i suppose
A few people have dogs so they would be walking Growlithes, Houndours, Electrike line, and Snubbulls.
Lopunnys and Bunearys. A house up the road has chickens... is there actually a chicken pokemon yet? Torchic and Combusken?
I once had Chinchillas =] so Chiramii once lived here.
Bug life... Caterpie line, Weedle line, Ledyba line, Spinarak line (lots of), Combee line, Wurmple line, Venomoth at night, Nincadas purely to represent the vast assortment of beetles found in my garden but obviously no Cicadas and i guess the Burmy line for Mothim but i've not seen things resembling a burmy before.
If 5th gen has a woodlouse pokemon there would be ooodles and OODLES of those... seriously we have tonnes of the things! Oh Slugma and Magcargo... lots of slugs and snails
Oh and all the poison types would have weakened poison to hurt thier prey only as there is nothing deadly to humans in Scotland unless you're allergic.
Plant life - Bellossom, oddish, Paras, Tangela, Hoppip line, Seedot line, Shroomish, Breloom, Budew line,
Bird life - Wingulls... lots and lots and lots and lots of flipping Wingulls!!! One of the reasons i disliked the 3rd gen games at first was because i was sick enough of seagulls in real life then i get plagued by them in a game! No pellipers though. No pelicans you see.
Many Mamepatos, Pidgeys, Starlys, some taillow and swellow (especially on springwatch haha), lots of Murkrows, many Spearows, the occasional Hoothoot and Noctowl (hear them but never see them). Since Natu is very small and we get small birds like Bluetits i will also say the occasional Natu will appear.
Not a bird but sometimes, very rarely i see bats so Zubats also... Very ironic considering they are stupidly common in game.
Rodent life - well i get the occasional field mouse so i will say Plusle, Minun, Pichu and pickachu not ratatta as i never see any rat in my garden. Pachirisu as it is the only Squirrel option and i have one bounding around my garden at the moment... likes my window sill.
Oh we'd also get Shaymin land forme as there is alot of hedgehogs. I'd have put sandshrew and sandslash but it would be too damp for them here what with their ground typing and all. Shaymin hogs with their grass typing would love it here.
Just a damn shame that i usually see them splattered, mushed and flattened on the road.
So venturing away from my garden i know there are bunearys and pretty much all the same birds and insects/arachnids etc.
However i think frogs and the such like can live here so poliwags and politoeds.
Vulpix and Ninetails roam the streets. Miltank, Mareep, Flaaffy and Tauros roam the fields. There's a horse place aswell so Ponytas.
Then we get to the beach and the Sea. So
Magikarps, possibly feebas futher out.
Krabby, Kingler, Corphish line, small fish so i can only think of barboach or remoraid for that. Lileeps, Cradilys, anoriths, Psyducks, Seel, Spheal, Sealeo, Farfetch'd, Shellder (lots of muscles), Staryu line, surskits, shellos and gastrodon.
I am going to say wailmer aswell as it is the closest thing to a dolphin at the current moment and the occasional dolphin is seen in the sea. I think we also have sandtiger sharks so Sharpedo also.
If i lived way up north in Orkney or something i would ahve the rare possibility of seeing a Kyogre as Orca whales have been sighted there.
Now every summer the fun fair/shows/market whatever you want to call it comes to Burntisland and i assume it would attract things like Ratatta, Koffing, Grimer as it creates a lot of smoke and alot of food is dropped.
Oh and Ratatta and Raticate can be found in the new housing estates where an aluminium factory used to be and when it got demolished people at the other end of the town were finding rats in their drawers and whatnot =P
Before that place got demolished possibly Magnemites, Voltorb and geodudes from the red rock could be found.
There's a hill in my town called the Binn, Up there i'd imagine more pachirisus, Stantler, Geodudes, Onix, Pidgeotto, Pidgeots and Stataptor. Maybe Woopers and Quagsires as it gets muddy.
Out in the sea again there is a lighthouse so an Ampharos must be there =P
Wow so many animals to think about!