How about if i give you list of some large DLS layouts...
Cajon Pass Xtreme
Florida East Coast Railway
V&O Afton Division
and to answer your question, there is no filter that i know of.
And large Non-DLS routes include...
Patriot Rives Lines V2 (montanawestern, find on TrainzForge, excellent route)
Reading & Northern (Josh Drumm, find on Jointed Rail.com)
BNSF Clovis Sub (Find on Dermmy's Checkrail)
East Kentucky Three (Find on Checkrail)
Midwest Grain 3 (JointedRail)
Mojave Sub (Built-In, TS12)
The ECML (Built-In, TS12)
Montana Rail Link (TrainzProRoutes, at one point was largest ever Trainz route, not sure now)
All of the UMR series (some on DLS, some on other various sites---just google)
BNSF Central Valley Division (forget where this is from, i'll check)
Southern China (TS12 built-in)
Avery-Drexel (TS10 built-in)
Balezino-Mosti (TS12 Built-In)
Marias Pass X (HPTrainz, payware)
Evansville Western Railway (Checkrail)
Austin Western East Sub (RRmods)
Muchinson 2 and Settle & Carstile (N3V DLC, payware)
and all of the roy's trainz routes (all pay ware, all super high quality)
And for un-realesed include...
Scratchy's Pittsburg Sub
The T:ANE routes (AT least two i can guarantee being very large)
TrainzForge' Horseshoe Curve (Basically Pittsburg Sub in the 1930s)
Probably others, as i just stated USA and a britan and canada route... just the ones i know off the top of my head...
EDIT: Links!
www.jointedrail.com
http://checkrail.com
http://trainzforge.weebly.com
http://www.roystrainz.com
http://rrmods.com (UMR 2010 and AWRR)
http://www.trainzproroutes.org
http://www.simulatorcentral.com