Okay, since I have lived in all parts of the Hoosier State and feel I am not biased toward or against any particular region of it, here is MY take on the hierarchy for Indiana freeways (all Interstates, and those longer than 4 miles along U.S. Highways & Indiana State Roads). Included are my explanations as to why I rank them the way I do (please feel free to disagree), and to which segments the rankings apply (for routes that are only freeways in segments or overlap other shielded routes).
#1: Interstate 465 (Indianapolis beltway) : Without this route, almost the entire Interstate system in Indiana collapses. Carries part of I-74 (and soon, part of I-69 as well), and provides redundancy for the "inner belt" sections of I-65 & I-70. Also carries all "through" U.S. Highways and State Roads. Has 10 (soon to be 11) system interchanges and several other significant ones.
#2: Interstates 80 & 94 (Tri-State Highway & Borman "Expressway" between IN Toll Road & Illinois state line) : Major toll-free gateway to Chicago from points south, east, and northeast.
#3: Interstate 70 (entire length) : Transcontinental Interstate & successor to the National Road (US 40). Connects west to St. Louis, Kansas City, Denver & beyond, as well as east to Columbus (OH), Baltimore & Washington, DC.
#4: Interstate 65 (entire length) : Transcontinental Interstate connecting north to Chicagoland & south to Louisville, Nashville (TN), and beyond.
#5: Interstate 69 (entire length) : Transcontinental Interstate (someday) connecting Indiana's two largest cities, most populous area of Michigan, and soon south to Evansville, Memphis & beyond.
#6: Indiana Toll Road (I-90 for entire length & I-80 for most) : Major transcontinental Interstates. Connects South Bend/Elkhart with Chicago to the west & Toledo and Cleveland to the east.
#7: Interstate 94 (Tri-State Highway between IN Toll Road & MI state line) : Part of major corridor connecting Chicago and Detroit; Michigan's gateway to the Chicagoland region.
#8: Saint Joseph Valley Parkway (US 31, US 20/31, and US 20) : Bypass route around South Bend and Elkhart. Portion of this freeway may be included in a future Interstate 67 between Indianapolis and Grand Rapids.
#9: Interstate 74 (entire length) : Significant Interstate corridor connecting the Mid-State cities of Illinois & the Quad-Cities of IL & IA to the west and Cincinnati to the east.
#10: U.S. Highway 31 (Hamilton County freeway section) : This 17-mile freeway serves rapidly growing Indy suburbs of Carmel & Westfield, and is along the path of a future I-67 corridor to South Bend and beyond.
#11: Interstate 64 (entire length) : Less relevant to most Hoosiers than other 2di-Interstates due to its rural, southern Indiana route, it nonetheless connects Louisville and Saint Louis, and provides (for now at least) a toll-free Interstate freeway crossing of the Ohio River in the Louisville area.
#12: Interstate 469 : Fort Wayne's semi-beltway provides important non-urban connections for several U.S. Highways. Construction of a system interchange with the U.S. 24 "Fort to Port" freeway will soon be underway.
#13: Interstate 265 / State Road 265 (future I-265) : Indiana portions of Louisville's outer beltway is at long last complete with the (tolled) Lewis & Clark Bridge over the Ohio River.
#14: U.S. Highway 31 (Plymouth to South Bend section) : Potentially part of a future Interstate 67, this freeway connects U.S. 30 at Plymouth to the South Bend area.
#15: Interstate 865 : The former "dogleg" of I-465, this important link (or glorified ramp, as some insist) provides the directional connections missing from the north junction of I-65 and I-465.
#16: U.S. Highway 31 (Kokomo Bypass section) : Provides the long-desired full-freeway bypass of Kokomo (previously called "Stoplight City") for U.S. 31, and a portion of U.S. 35. Potentially part of a future I-67 between Indianapolis, South Bend, and western MI).
#17: U.S. Highway 24 (Fort to Port freeway) : This freeway bypassed a crooked, dangerous, and congested routing of U.S. Highway 24 that hugged the Maumee River between New Haven and the Ohio state line northeast of Woodburn.
#18: Keystone Parkway (née Keystone Avenue - former IN State Road 431 in Hamilton Co.) : this sub-Interstate grade freeway runs through the densely populated Indianapolis suburb of Carmel (roundabout capital of the world). It's origin point (at the city/county line along 96th Street) is at present being converted into another roundabout interchange.
#19: Interstate 275 (Cincinnati (OH) beltway) : The least significant Interstate in Indiana, as it barely dips into the state.
#20: State Road 641 (Terre Haute bypass) : Because it's interchange with I-70 is not a freeway-to-freeway junction, this long-desired connection to U.S. 41 is not that significant statewide.
#21: State Road 912 (Cline Avenue) : Ranked low due to the fact that it's been discontinuous since the bridge over the ship channel was closed. Once reconnected, I would consider ranking it higher, assuming full-freeway status is maintained.
#22: Shadeland Avenue (former State Road 100 from I-465 to Washington Street) : This remnant of Indy's original bypass remains a sub-standard stub freeway, but functions more as the urban arterial it becomes north of the deficient Washington Street (old U.S. 40) cloverleaf.
BTW, I did NOT include Interstate 80 independently in this list, as it is NOT concurrent with other Interstates only for the very short stretch between the IN Toll Road (I-90) & the Tri-State Hwy (I-94). Also, the Sam Jones Expressway in Indianapolis was not included since it's junction with I-465 has been downgraded from a system to a service interchange and the remaining freeway portion is both sub-standard and too short to meet my 4-mile minimum length criteria.
Okay, that's it, so flame away at my rankings!