This is an interesting discussion, and there are stats on this topic. To take it easy on my brain, I'm doing MSA only
Massachusetts/New Hampshire (Bostons MSA) - Top City Pairs by Ridership 2017
**Only included the main Boston Amtrak Stations IN the city, or the ones in the MSA going to NYC**
1. Boston to NYC
2. Boston Back Bay to NYC
3. Route 128 to NYC
4. Boston to Providence
5. Boston North to Portland
6. Boston to Stamford
7. Boston Back Bay to Providence
8. Boston North to Exeter
9. Boston to New Haven
10. Boston North to Wells
Massachusetts/New Hampshire (Boston MSA) - Station Ridership Numbers 2017
Boston - 1,542,975
Boston Back Bay - 618,101
Route 128 - 442,406
Boston North - 432,818
Exeter - 84,215
Dover - 59,059
Durham - 58,803
Haverhill - 44,827
Woburn - 18,953
Framingham - 1,954
Total Boston MSA Ridership: 3,304,111
https://www.railpassengers.org/site/...es/1194/ma.pdf
https://www.railpassengers.org/site/...es/1202/nh.pdf
Pennsylvania/Delaware/New Jersey (Philadelphia MSA) - Top City Pairs by Ridership 2017
**Only included the main Philly Amtrak Stations IN the city, or the ones in the MSA going to NYC**
PA
1. Philadelphia to NYC
2. Philadelphia to Washington DC
5. Philadelphia to Baltimore
7. Philadelphia to Newark, NJ
9. Paoli to NYC
10. Philadelphia to BWI Airport
DE
1. Wilmington to NYC
5. Wilmington to Newark, NJ
7. Wilmington to Metropark, NJ
NJ
3. Trenton to NYC (station technically in NYC CSA, but at least half of the ridership is from Philly MSA residents)
Pennsylvania/New Jersey/Delaware (Philly MSA) - Station Ridership Numbers 2017
Philadelphia - 4,340,135
Wilmington - 679,758
Paoli - 216,048
Exton - 149,744
Downingtown - 86,806
Ardmore - 65,882
Parkesburg - 44,568
Coatesville - 17,770
Newark, DE - 13,614
Cornwells Heights - 3,073
North Philadelphia - 1,037
Total Philadelphia MSA Ridership: 5,618,435
https://www.railpassengers.org/site/...es/1211/pa.pdf
https://www.railpassengers.org/site/...es/1181/de.pdf
For Philly, there is also:
Trenton - 430,952 riders
One could reasonably count HALF of these riders as Philadelphia MSA residents. Trenton is directly across the river from Bucks County, PA, which is the Philly MSA, but Trenton is in Mercer County, NJ, which is technically the NYC CSA. A lot of people who live in Bucks County commute to NYC and the surrounding area for work, but live in Bucks County for the lower taxes.
https://www.railpassengers.org/site/...es/1203/nj.pdf